[Federal Register Volume 87, Number 218 (Monday, November 14, 2022)]
[Notices]
[Pages 68236-68268]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-24493]
[[Page 68235]]
Vol. 87
Monday,
No. 218
November 14, 2022
Part II
Department of Commerce
-----------------------------------------------------------------------
National Oceanic and Atmospheric Administration
-----------------------------------------------------------------------
Endangered and Threatened Wildlife and Plants; 12-Month Finding on a
Petition To List the Shortfin Mako Shark (Isurus oxyrinchus) as
Threatened or Endangered Under the Endangered Species Act; Notice
Federal Register / Vol. 87 , No. 218 / Monday, November 14, 2022 /
Notices
[[Page 68236]]
-----------------------------------------------------------------------
DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[Docket No. 221103-0232; RTID 0648-XR116]
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition To List the Shortfin Mako Shark (Isurus oxyrinchus) as
Threatened or Endangered Under the Endangered Species Act
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Department of Commerce.
ACTION: Notice of 12-month finding and availability of status review
document for the shortfin mako shark (Isurus oxyrinchus).
-----------------------------------------------------------------------
SUMMARY: We, NMFS, have completed a comprehensive status review under
the Endangered Species Act (ESA) for the shortfin mako shark (Isurus
oxyrinchus) in response to a petition from Defenders of Wildlife to
list the species. After reviewing the best scientific and commercial
data available, including the Status Review Report, we have determined
that listing the shortfin mako shark as a threatened or endangered
species under the ESA is not warranted.
DATES: This finding was made on November 14, 2022.
ADDRESSES: The Status Review Report associated with this determination,
its references, and the petition can be accessed electronically online
at: https://www.fisheries.noaa.gov/species/shortfin-mako-shark#conservation-management.
FOR FURTHER INFORMATION CONTACT: Adrienne Lohe, NMFS Office of
Protected Resources, 301-427-8442.
SUPPLEMENTARY INFORMATION:
Background
On January 25, 2021, we received a petition from Defenders of
Wildlife to list the shortfin mako shark (Isurus oxyrinchus) as a
threatened or endangered species under the ESA. The petition asserted
that the shortfin mako shark is threatened by four of the five ESA
section 4(a)(1) factors: (1) the present or threatened destruction,
modification, or curtailment of its habitat or range; (2)
overutilization for commercial and recreational purposes; (3)
inadequacy of existing regulatory mechanisms; and (4) other natural or
manmade factors.
On April 15, 2021, NMFS published a 90-day finding for the shortfin
mako shark with our determination that the petition presented
substantial scientific and commercial information indicating that the
petitioned action may be warranted (86 FR 19863). We also announced the
initiation of a status review of the species, as required by section
4(b)(3)(A) of the ESA, and requested information to inform the agency's
decision on whether this species warrants listing as endangered or
threatened under the ESA. We received information from the public in
response to the 90-day finding and incorporated the information into
both the Status Review Report (Lohe et al. 2022) and this 12-month
finding.
Listing Determinations Under the ESA
We are responsible for determining whether species are threatened
or endangered under the ESA (16 U.S.C. 1531 et seq.). To be considered
for listing under the ESA, a group of organisms must constitute a
``species,'' which is defined in section 3 of the ESA to include any
subspecies of fish or wildlife or plants, and any distinct population
segment (DPS) of any species of vertebrate fish or wildlife which
interbreeds when mature (16 U.S.C. 1532(16)). On February 7, 1996, NMFS
and the U.S. Fish and Wildlife Service (USFWS; together, the Services)
adopted a policy describing what constitutes a DPS of a taxonomic
species (``DPS Policy,'' 61 FR 4722). The joint DPS Policy identifies
two elements that must be considered when identifying a DPS: (1) The
discreteness of the population segment in relation to the remainder of
the taxon to which it belongs; and (2) the significance of the
population segment to the remainder of the taxon to which it belongs.
Section 3 of the ESA defines an endangered species as any species
which is in danger of extinction throughout all or a significant
portion of its range and a threatened species as one which is likely to
become an endangered species within the foreseeable future throughout
all or a significant portion of its range (16 U.S.C. 1532(6), 16 U.S.C.
1532(20)). Thus, in the context of the ESA, we interpret an
``endangered species'' to be one that is presently in danger of
extinction. A ``threatened species,'' on the other hand, is not
presently in danger of extinction, but is likely to become so in the
foreseeable future. In other words, the primary statutory difference
between a threatened and endangered species is the timing of when a
species is in danger of extinction, either presently (endangered) or in
the foreseeable future (threatened).
Under section 4(a)(1) of the ESA, we must determine whether any
species is endangered or threatened as a result of any one or a
combination of any of the following factors: (A) the present or
threatened destruction, modification, or curtailment of its habitat or
range; (B) overutilization for commercial, recreational, scientific, or
educational purposes; (C) disease or predation; (D) the inadequacy of
existing regulatory mechanisms; or (E) other natural or manmade factors
affecting its continued existence (16 U.S.C. 1533(a)(1)). We are also
required to make listing determinations based solely on the best
scientific and commercial data available, after conducting a review of
the species' status and after taking into account efforts, if any,
being made by any state or foreign nation (or subdivision thereof) to
protect the species (16 U.S.C. 1533(b)(1)(A)).
Status Review
To determine whether the shortfin mako shark warrants listing under
the ESA, we completed a Status Review Report, which summarizes
information on the species' taxonomy, distribution, abundance, life
history, and biology; identifies threats or stressors affecting the
status of the species; and assesses the species' current and future
extinction risk. We appointed a biologist in the Office of Protected
Resources Endangered Species Conservation Division to compile and
complete a scientific review of the best available information on the
shortfin mako shark, including information received in response to our
request for information (86 FR 19863, April 15, 2021). Next, we
convened an Extinction Risk Analysis (ERA) Team of biologists and shark
experts to assess the threats affecting the shortfin mako shark, as
well as demographic risk factors (abundance, productivity, spatial
distribution, and diversity), using the information in the scientific
review. The Status Review Report presents the ERA Team's professional
judgment of the extinction risk facing the shortfin mako shark but
makes no recommendation as to the listing status of the species. The
Status Review Report is available electronically (see ADDRESSES).
Information from the Status Review Report is summarized below in the
Biological Review section, and the results of the ERA from the Status
Review Report are discussed below.
The Status Review Report was subject to independent peer review as
required by the Office of Management and Budget Final Information
Quality Bulletin for Peer Review (M-05-03; December 16, 2004). The
Status Review
[[Page 68237]]
Report was peer reviewed by three independent specialists selected from
the academic and scientific community with expertise in shark biology,
conservation, and management, and specific knowledge of shortfin mako
sharks. The peer reviewers were asked to evaluate the adequacy,
appropriateness, and application of data used in the Status Review
Report, as well as the findings made in the ``Assessment of Extinction
Risk'' section of the report. All peer reviewer comments were addressed
prior to finalizing the Status Review Report.
We subsequently reviewed the Status Review Report, its cited
references, and peer review comments, and conclude the Status Review
Report, upon which this 12-month finding is based, provides the best
available scientific and commercial information on the shortfin mako
shark. Much of the information discussed below on the species' biology,
distribution, abundance, threats, and extinction risk is attributable
to the Status Review Report. Following our review of the Status Review
Report and consideration of peer review comments, we conclude, however,
that the ERA Team's foreseeable future of 25 years for the shortfin
mako shark is not adequately justified. Each of the three peer
reviewers recommended evaluating the species' risk of extinction over a
longer time horizon. Based on these peer review comments and our review
of the ERA Team's selection of 25 years as the foreseeable future, we
have completed an independent determination of the foreseeable future
(see Extinction Risk Analysis). For this reason, while we rely on the
ERA Team's assessment of the species' present risk of extinction, we
have supplemented the assessment of the species' risk of extinction
within the foreseeable future. We have also independently applied the
statutory provisions of the ESA, including evaluation of the factors
set forth in section 4(a)(1)(A)-(E), our regulations regarding listing
determinations,\1\ and relevant policies identified herein in making
the 12-month finding determination.
---------------------------------------------------------------------------
\1\ On July 5, 2022, the United States District Court for the
Northern District of California issued an order vacating the ESA
section 4 implementing regulations that were revised or added to 50
CFR 424 in 2019 (``2019 regulations,'' see 84 FR 45020, August 27,
2019) although making no findings on the merits. On September 21,
2022, the U.S. Court of Appeals for the Ninth Circuit granted a
temporary stay of the district court's July 5 order. As a result,
the 2019 regulations are once again in effect, and we are applying
the 2019 regulations here. For purposes of this determination, we
considered whether the analysis or its conclusions would be any
different under the pre-2019 regulations. We have determined that
our analysis and conclusions presented here would not be any
different.
---------------------------------------------------------------------------
Biological Review
Taxonomy and Species Description
The shortfin mako shark belongs to the family Lamnidae in the order
Lamniformes, the mackerel sharks (ITIS 2021). Lamnid sharks are
littoral to epipelagic with broad distributions in tropical to cold-
temperate waters (Compagno 1984). They are fast-swimming and have a
modified circulatory system to maintain internal temperatures warmer
than the surrounding water (Compagno 1984). The shortfin mako shark
belongs to the genus Isurus and only has a single living cogeneric
species, the longfin mako shark (Isurus paucus). The species is
relatively large, reaching a maximum total length (TL) of about 445
centimeters (cm) (Weigmann 2016), and has a moderately slender,
spindle-shaped body with a conical snout (Compagno 1984). Its pectoral
fins are narrow-tipped and moderately broad and long (considerably
shorter than the length of the head) as compared to the very long
pectoral fins of the longfin mako shark, which also has a less pointed
snout and dusky underside (Compagno 1984; Ebert et al. 2013). The first
dorsal fin is large and the second is very small and pivoting (Compagno
1984). The upper and lower lobes of the caudal fin are of nearly equal
size, which is reflected in the genus name Isurus from the Greek words
for ``equal tail.'' The teeth are large and bladelike without
serrations, and the tips of the anterior teeth are strongly reflexed
(Compagno 1984). The dorsal surface of the body is dark blue and the
ventral side is white (Compagno 1984).
Distribution
The shortfin mako shark is a globally distributed pelagic species,
occurring across all temperate and tropical ocean waters from about
50[deg] N (up to 60[deg] N in the northeast Atlantic) to 50[deg] S and
across a range of marine habitats (Rigby et al. 2019; Santos et al.
2020). Compagno (2001) provides the following description of the
species' global distribution: in the western Atlantic, the species
occurs from the Gulf of Maine to southern Brazil and possibly northern
Argentina, including Bermuda, the Caribbean, and the Gulf of Mexico. In
the eastern Atlantic, the range spans from Norway, the British Isles,
and the Mediterranean to Morocco, Azores, Western Sahara, Mauritania,
Senegal, C[ocirc]te d'Ivoire, Ghana, southern Angola, probably Namibia,
and the west coast of South Africa. In the Indo-Pacific basin, the
species is found from the east coast of South Africa, Mozambique,
Madagascar, Mauritius and Kenya north to the Red Sea, and east to
Maldives, Iran, Oman, Pakistan, India, Indonesia, Viet Nam, China,
Taiwan, North Korea, South Korea, Japan, Russia, Australia (all states
and entire coast except for Arafura Sea, Gulf of Carpentaria and Torres
Strait), New Zealand (including Norfolk Island), New Caledonia, and
Fiji. In the central Pacific, the shortfin mako shark occurs from south
of the Aleutian Islands to the Society Islands, including the Hawaiian
Islands, and in the eastern Pacific, from southern California (and
sometimes as far north as Washington State) south to Mexico, Costa
Rica, Ecuador, Peru, and central Chile. Rare observations outside of
this range have also been made, for example in waters of British
Columbia (Gillespie and Saunders 1994).
Habitat Use
The shortfin mako shark is known to travel long distances in and
between open ocean, continental shelf, shelf edge, and shelf slope
habitats (Rogers et al. 2015b; Santos et al. 2021), making extensive
long-distance straight-line movements of several thousand kilometers
(km) (Francis et al. 2019). From traditional dart and fin tagging data,
maximum recorded time at liberty is 12.8 years, and the maximum
straight-line distance between tag and recapture localities is 3,043
nautical miles (5,636 km) (Kohler and Turner 2019). Shorter-term
electronic tagging results from several studies indicate that the
species commonly makes roundtrip migratory movements of more than
20,000 km, with one individual found to undertake an extended migration
of 25,550 km over a period of 551 days (Rogers et al. 2015b; Francis et
al. 2019). While the species has also demonstrated fidelity to small
geographic areas on or near continental shelves and coastal areas of
high productivity, this fidelic behavior is rarely observed in the open
ocean (Rogers et al. 2015b; Corrigan et al. 2018; Francis et al. 2019;
Gibson et al. 2021). Recent research demonstrates that the species
regularly switches between these states of activity (i.e., resident or
fidelity behavior state and traveling state), spending nearly half
their time (44-47 percent) in residency and slightly less than half
their time (35-42 percent) in transit (Rogers et al. 2015b; Francis et
al. 2019). It is unknown whether these behavioral states are tied to
specific behaviors such as feeding or breeding. Furthermore, this
behavioral switching may be affected by factors including
[[Page 68238]]
environmental variation, spatial areas of sampling, or biotic factors;
therefore, these findings may not be representative of the entire
species, especially across time and space.
The vertical distribution of shortfin mako sharks is related to
numerous environmental variables, including water temperature,
dissolved oxygen (DO) concentration, time of day, prey availability,
and lunar phase. The species typically occupies waters ranging between
17 [deg]C and 22 [deg]C (Casey and Kohler 1992; Nasby-Lucas et al.
2019; Santos et al. 2020, 2021), though it has a broad thermal
tolerance and has been shown to also occupy waters from 10 [deg]C
(Abascal et al. 2011) to 31 [deg]C (Vaudo et al. 2017). Like other
lamnid sharks, the shortfin mako shark has counter-current circulation
and is a red muscle endotherm, meaning that it can maintain the
temperature of its slow-twitch, aerobic red muscle significantly above
ambient temperature (Watanabe et al. 2015). Red muscle endothermy
allows the species to tolerate a greater range of water temperatures,
cruise faster, and have greater maximum annual migration lengths than
fish without this trait (Watanabe et al. 2015). The high energetic cost
of endothermy is suggested to be outweighed by benefits such as
increased foraging success, prey encounter rates, and access to other
seasonally available resources (Watanabe et al. 2015). The routine
metabolic rate and maximum metabolic rate of shortfin mako sharks is
among the highest measured for any shark species (Sepulveda et al.
2007), which may explain why the shortfin mako shark typically inhabits
waters with DO concentrations of at least 3 milliliters per liter and
avoids areas of low DO (Abascal et al. 2011). Individuals primarily
occupy the upper part of the water column, but dive to depths of
several hundred meters (m) (as deep as 979.5 m reported by Santos et
al. (2021)), allowing them to forage for mesopelagic fishes and squid,
though dives may have other functions including navigation (Holts and
Bedford 1993; Francis et al. 2019). There is evidence that illumination
from a full moon causes shortfin mako sharks to move into deeper water
in pursuit of prey (Lowry et al. 2007). ``Bounce'' or ``yo-yo'' diving
behavior, in which individuals repeatedly descend to deeper water and
then ascend to shallow depths, has been regularly observed in both
adults and young-of-the-year (YOY) (Sepulveda et al. 2004; Abascal et
al. 2011; Vaudo et al. 2016; Santos et al. 2021). This type of diving
behavior may be associated with feeding, behavioral thermoregulation,
energy conservation, and navigation (Klimley et al. 2002; Sepulveda et
al. 2004). Tagging studies have shown that the species typically spends
more time in deeper, colder water during the daytime, and moves to
shallower, warmer waters at night (Holts and Bedford 1993; Klimley et
al. 2002; Sepulveda et al. 2004; Loefer et al. 2005; Stevens et al.
2010; Abascal et al. 2011; Nasby-Lucas et al. 2019). These diel
vertical migrations are typically attributed to the pursuit of prey.
However, other studies indicate no significant changes in vertical
distribution between daytime and nighttime (Abascal et al. 2011, Santos
et al. 2020). Larger individuals can dive to deeper depths than smaller
individuals (Sepulveda et al. 2004), and juveniles specifically tend to
spend much of their time in shallower, warmer water (Holts and Bedford
1993; Nosal et al. 2019).
There is some evidence that certain ocean currents and features may
limit movement patterns, including the Mid-Atlantic ridge separating
the western and eastern Atlantic (Casey and Kohler 1992 using
conventional tagging data from 231 recaptured shortfin mako sharks over
a 28-year period; Santos et al. 2020 using satellite telemetry for 41
shortfin mako sharks over a period of between 30 and 120 days), and the
Gulf Stream separating the North Atlantic and the Gulf of Mexico/
Caribbean Sea (Vaudo et al. 2017 using satellite telemetry for 26
shortfin mako sharks over a period of 78-527 days). However,
conventional tagging data indicates that movement does occur across
these features. Data from the NMFS Cooperative Shark Tagging Program
(n=1,148 recaptured shortfin mako sharks) over a 52-year period show
evidence of the species crossing the Mid-Atlantic Ridge demonstrating
exchange between the western and eastern Atlantic (Kohler and Turner
2019). In fact, individual shortfin mako sharks (n = 104) that made
long distance movements (>1,000 nautical miles) while at liberty for
less than one year were primarily tagged off the coast of the U.S.
Northeast and were recaptured in the Gulf of Mexico, Caribbean Sea,
mid-Atlantic Ocean, and off Portugal, Morocco, and Western Sahara
(Kohler and Turner 2019). In the Pacific, tagging data supports east-
west mixing in the north and minimal east-west mixing in the south
(Sippel et al. 2016 using conventional tagging data from 704 recaptured
shortfin mako sharks since 1968; Corrigan et al. 2018 using satellite
telemetry data of 13 individuals over a period of 249-672 days). Trans-
equatorial movement appears to be uncommon based on tagging studies
(Sippel et al. 2016; Corrigan et al. 2018), but tagged shortfin mako
sharks have been recorded crossing the equator (Rogers et al. 2015a;
Santos et al. 2021).
The locations of mating grounds and other reproductive areas are
not well known for the shortfin mako shark, although the distribution
of the youngest age classes may indicate potential pupping and nursery
areas. Casey and Kohler (1992) observed YOY shortfin mako sharks
offshore in the Gulf of Mexico, hypothesizing that pups are born
offshore in the Northwest Atlantic to protect them from predation by
large sharks, including other makos. Bite marks observed on mature
females caught in the Gulf of Mexico may have resulted from mating
behavior, indicating that the area may also be a mating ground (Gibson
et al. 2021). The presence of mature and pregnant females in the Gulf
of Mexico provides further support that this may be a gestation and
parturition ground for the species. However, fisheries data suggests
that pupping is geographically widespread in the Northwest Atlantic
given that neonates are widely distributed along the coast of North
America and largely overlap with the distribution of older immature
sharks and adults (Natanson et al. 2020). Excursions of tagged shortfin
mako sharks towards the shelf and slope waters of the Subtropical
Convergence Zone, the Canary archipelago, and the northwestern African
continental shelf, as well as aggregations of YOY shortfin mako sharks
in these areas, may indicate that they serve as pupping or nursery
grounds in the Northeast Atlantic (Maia et al. 2007; Natanson et al.
2020; Santos et al. 2021). In the Eastern North Pacific, the Southern
California Bight has been suggested as a nursery area as roughly 60
percent of the catch here is made up by YOY and 2- to 4-year-old
juveniles (Holts and Bedford 1993; Rodr[iacute]guez-Madrigal et al.
2017; Nasby-Lucas et al. 2019). Farther south, the presence of many
juveniles and some neonates near fishing camps in Baja California,
Mexico, suggests that the area between Bah[iacute]a Magdalena and
Laguna San Ignacio may also be a nursery ground for the shortfin mako
shark (Conde-Moreno and Galvan-Magana 2006). Presence of small immature
shortfin mako sharks off Caldera, Chile, suggests that this may be a
pupping or nursery area for the Southeastern Pacific (Bustamante and
Bennett 2013). The temperate waters of the south-west Indian Ocean have
been shown to host high concentrations of
[[Page 68239]]
neonates and adults, suggesting that this area may be a nursery ground
(Wu et al. 2021). Further, pregnant females have been observed in
coastal waters off South Africa, strengthening the evidence that this
area may be used for pupping or as a nursery (Groeneveld et al. 2014).
Diet and Feeding
The shortfin mako shark is a large, active predator that feeds
primarily on teleosts and also consumes cephalopods, other
elasmobranchs, cetaceans, and crustaceans (Stillwell and Kohler 1982;
Cort[eacute]s 1999; Maia et al. 2006; Gorni et al. 2012). It is
estimated that shortfin mako sharks must consume 4.6 percent of their
body weight per day to meet their high energetic demands (Wood et al.
2009). Based on the shortfin mako shark's diet, the species has a
trophic level of 4.3 out of 5.0 (tertiary consumers have a trophic
level over 4.0, while plants have a trophic level of one), one of the
highest of 149 species examined by Cort[eacute]s (1999) and comparable
to other pelagic shark species such as common and bigeye thresher
sharks (Alopias vulpinus and Alopias superciliosus), the salmon shark
(Lamna ditropis), and the oceanic whitetip shark (Carcharhinus
longimanus) (Bizzarro et al. 2017). Rogers et al. (2012) found evidence
that the species targets specific prey despite high prey diversity;
however, stable isotope analysis indicates that the species is a
generalist predator (Maya Meneses et al. 2016). The degree of prey
selectivity in any given individual's diet is likely strongly
correlated with prey availability, with prey being consumed as
encountered.
The specific diet of the shortfin mako shark varies by life stage,
geographic location, season, and oceanic habitat. In the Northwest
Atlantic, bluefish (Pomatomus saltatrix) are a major inshore prey item
for the species and have been estimated to make up 77.5 percent of diet
by volume (Stillwell and Kohler 1982), and more recently, 92.6 percent
of diet by weight (Wood et al. 2009). In the northeast Atlantic,
teleosts made up over 90 percent of the species' diet by weight, and
Clupeiformes and garpike (Belone belone) are common prey (Maia et al.
2006). In the South Atlantic, teleosts are also dominant in the
shortfin mako shark's diet (including Lepidocibium flavobruneum,
Scomber colias, and Trichiruridae), while cephalopods of the orders
Teuthida and Octopoda are also consumed (Gorni et al. 2012). In the
northeast Pacific along the west coast of the United States, jumbo
squid (Dosidicus gigas) and Pacific saury (Cololabis saira) are the two
most important prey items, and other frequent teleost prey includes
Pacific sardine (Sardinops sagax), Pacific mackerel (Scomber
japonicus), jack mackerel (Trachurus symmetricus), and striped mullet
(Mugil cephalus) (Preti et al. 2012). By contrast, YOY and juvenile
shortfin mako sharks off Baja California Sur, Mexico, largely consume
whitesnout searobin (Prionotus albirostris), Pacific mackerel (S.
japonicus), and a variety of small squids (Velasco Tarelo 2005). As
they age, larger teleost species and squids more commonly found in
offshore pelagic waters become increasingly important, as evidenced by
stable isotope analysis (Velasco Tarelo 2005). A large female shortfin
mako shark recreationally caught off the coastline of the Southern
California Bight was found to have eaten a California sea lion,
Zalophus californianus, an event that does not appear uncommon based on
previously documented pinnipeds in the stomachs of large shortfin mako
sharks (Lyons et al. 2015). Shortfin mako sharks in the Indian Ocean
prey on teleosts (Trachurus capensis and S. sagax), elasmobranchs
(Rhizoprionodon acutus and Carcharhinus obscurus), and cephalopods
(Loligo spp.) (Groeneveld et al. 2014). The dominant prey of shortfin
mako sharks caught in coastal bather protection nets in the southwest
Indian Ocean were elasmobranchs, while the diet of shortfin mako sharks
caught in offshore longlines was dominated by teleosts (Groeneveld et
al. 2014). As the size of individuals caught in coastal bather nets was
significantly greater than those caught in offshore longlines,
Groeneveld et al. (2014) suggest that larger prey attracts larger mako
sharks to coastal waters.
Size and Growth
Shortfin mako sharks are long-lived, and are estimated to reach
maximum ages of at least 28-32 years based on vertebral band counts
validated by bomb radiocarbon and tag-recapture studies (Natanson et
al. 2006; Dono et al. 2015). Longevity in the Pacific has been
estimated as high as 56 years (Chang and Liu 2009; Carreon-Zapiain et
al. 2018). There is uncertainty in the use of vertebral band pair
counting to determine age as some authors find evidence for or assume
annual growth band deposition periodicity (Cailliet et al. 1983;
Campana et al. 2002; Ardizzone et al. 2006; Bishop et al. 2006; Semba
et al. 2009; Dono et al. 2015; Liu et al. 2018) while others find
evidence for the deposition of two growth band pairs each year for
either all (Pratt Jr. and Casey 1983) or their first five years of life
(Wells et al. 2013). Kinney et al. (2016) used the recapture of an
oxytetracycline-tagged adult male to validate annual band deposition in
adult shortfin mako sharks, inferring that juveniles experience more
rapid growth and, therefore, exhibit biannual band pair deposition. In
addition, there is evidence that vertebral band pair counts do not
accurately reflect age in older, large individuals (Harry 2018;
Natanson et al. 2018). Due to inconsistent information on vertebral
band deposition in the Pacific, the International Scientific Committee
for Tuna and Tuna-like Species (ISC) Shark Working Group's 2018 stock
assessment of shortfin mako sharks in the North Pacific treated data
from the western North Pacific as having a constant band pair
deposition rate and data from the eastern North Pacific as having a
band pair deposition rate that changes from two to one band pairs per
year after age 5. The 2017 stock assessment of North and South Atlantic
shortfin mako sharks conducted by the International Commission for the
Conservation of Atlantic Tunas (ICCAT) assumed annual band pair
deposition based on Natanson et al. (2006).
Shortfin mako sharks exhibit slow growth rates. Growth coefficient
(K) estimates range from 0.043-0.266 year-\1\ in the
Atlantic Ocean, 0.0154-0.16 year-\1\ in the Pacific Ocean,
and 0.075-0.15 year-\1\ in the Indian Ocean (Pratt Jr. and
Casey 1983, Ribot-Carballal et al. 2005, Natanson et al. 2006, Bishop
et al. 2006, Cerna and Licandeo 2009, Semba et al. 2009, Groeneveld et
al. 2014, Liu et al. 2018). Males and females have similar growth rates
until a certain point, when male growth slows down compared to female
growth. This has been estimated to occur at 7 years of age in the
western and central North Pacific (Semba et al. 2009), 11 years of age
in the Northwest Atlantic (Natanson et al. 2006), and 15 years of age
(217 cm fork length (FL)) in the western South Atlantic (Dono et al.
2015). Females ultimately attain larger sizes than males, as has been
documented in other shark species (Natanson et al. 2006). Maximum
theoretical length in females is reported to be 370 cm TL in the
western and central North Pacific (Semba et al. 2009) and 362 cm TL in
the eastern North Pacific (Carreon-Zapiain et al. 2018). The maximum
observed length for the species is 445 cm TL (Weigmann 2016), although
Kabasakal and de Maddalena (2011) used photographs to estimate the
length of a female caught off Turkey at 585 cm TL.
Age and size at maturity vary by geographic location. In general,
males
[[Page 68240]]
and females reach maturity at approximately 6-9 and 15-21 years
(Natanson et al. 2006; Semba et al. 2009), and at sizes of 180-222 cm
TL and 240-289 cm TL (Conde-Moreno and Galvan-Magana 2006; White 2007;
Varghese et al. 2017), respectively. Additional information on growth
and reproductive parameters for the species can be found in Table 1 of
the Status Review Report.
Reproductive Biology
Shortfin mako sharks reproduce through oophagous (meaning `egg
eating') vivipary, wherein, after depletion of their yolk-sac, the
embryos develop by ingesting unfertilized eggs inside the mother's
uterus and are born as live young (Stevens 1983; Mollet et al. 2000).
Estimates of gestation time vary from nine months to 25 months (Mollet
et al. 2000; Duffy and Francis 2001; Joung and Hsu 2005; Semba et al.
2011) and litter sizes typically range from four to 25 pups (Mollet et
al. 2000; Joung and Hsu 2005; Semba et al. 2011). Several studies find
that litter size increases with maternal size (Mollet et al. 2000;
Semba et al. 2011), though others find no evidence of this relationship
(Joung and Hsu 2005; Liu et al. 2020). Size at birth is approximately
70 cm TL (Mollet et al. 2000). The reproductive cycle is estimated to
take up to 3 years, with a potential resting period of 18 months
(Mollet et al. 2000). There is evidence that parturition (birth) occurs
in late winter to mid-spring in both the Northern and Southern
Hemispheres based on embryonic growth estimates (Mollet et al. 2000;
Semba et al. 2011; Bustamante and Bennett 2013), though Duffy and
Francis (2001) found evidence of parturition in summer. With regard to
mating strategy, two studies have found genetic evidence for polyandry
and multiple paternity within litters, though other mating strategies
(e.g., polygyny or monogamy) cannot be ruled out (Corrigan et al. 2015;
Liu et al. 2020).
Population Structure and Genetics
Although certain ocean currents and features may limit movement
patterns between different regions as discussed previously (see Habitat
Use), several genetic studies indicate a globally panmictic
(characterized by random mating) population with some genetic
structuring among ocean basins.
Heist et al. (1996) investigated population structure using
restriction fragment length polymorphism analysis of maternally
inherited mitochondrial DNA (mtDNA) from shortfin mako sharks in the
Northwest Atlantic (n = 21), central North Atlantic (n = 24), western
South Atlantic (n = 23), eastern North Pacific (n = 30), and western
South Pacific (n = 22). The North Atlantic samples showed significant
isolation from other regions (p < 0.001) and differed from other
regions by the relative lack of rare and unique haplotypes and high
abundance of a single haplotype (Heist et al. 1996). Significant
differences in haplotype frequencies were not detected between the
samples from Brazil, Australia, and California (Heist et al. 1996).
Haplotypes did not seem to be confined to specific regions, and the
three most common haplotypes were found in all samples (Heist et al.
1996). Clustering of mtDNA haplotypes did not initially support the
presence of genetically distinct stocks of shortfin mako shark (Heist
et al. 1996); however, reanalysis of the data found significant
differentiation between the South Atlantic and North Pacific samples
(Schrey and Heist 2003) in addition to isolation of the North Atlantic.
A microsatellite analysis of samples from the North Atlantic (n =
152), South Atlantic (Brazil; n = 20), North Pacific (n = 192), South
Pacific (n = 43), and Atlantic and Indian coasts of South Africa (n =
26) found very weak evidence of population structure (FST =
0.0014, P = 0.1292; RST = 0.0029, P = 0.019) (Schrey and
Heist 2003). Pairwise FST comparisons were not statistically
significant after Bonferroni correction, though one pairwise
RST value (North Atlantic vs. North Pacific) showed
significant differentiation (RST = 0.0106, P = 0.0034).
These results were insufficient to reject the null hypothesis of a
single genetic stock of shortfin mako shark, suggesting that there is
sufficient movement of shortfin mako sharks, and therefore gene flow,
to reduce genetic differentiation between regions (Schrey and Heist
2003). The authors note that their findings conflict with the
significant genetic structure revealed through mtDNA analysis by Heist
et al. (1996). They suggest that as mtDNA is maternally inherited and
nuclear DNA is inherited from both parents, population structure shown
by mtDNA data could indicate that female shortfin mako sharks exhibit
limited dispersal and philopatry to parturition sites, while male
dispersal allows for gene flow that would explain the results from the
microsatellite data (Schrey and Heist 2003).
Taguchi et al. (2011) analyzed mtDNA samples from the central North
Pacific (n = 39), western South Pacific (n = 16), eastern South Pacific
(n = 10), North Atlantic (n = 9), eastern Indian Ocean (n = 16), and
western Indian Ocean (n = 16), finding evidence of significant
differentiation between the North Atlantic, and the central North
Pacific and eastern South Pacific (pairwise [Phi]ST = 0.2526
and 0.3237, respectively). Interestingly, significant structure was
found between the eastern Indian Ocean and the Pacific Ocean samples
(pairwise [Phi]ST values for Central North Pacific, Western
South Pacific, Eastern South Pacific are 0.2748, 0.1401, and 0.3721,
respectively), but not between the eastern Indian and the North
Atlantic (Taguchi et al. 2011).
Corrigan et al. (2018) also found evidence of matrilineal structure
from mtDNA data, while nuclear DNA data provide support for the
existence of a globally panmictic population. Although there was no
evidence of haplotype partitioning by region and most haplotypes were
found across many (sometimes disparate) locations, Northern Hemisphere
sampling locations were significantly differentiated from all other
samples, suggesting reduced matrilineal gene flow across the equator
(Corrigan et al. 2018). The only significant differentiation indicated
by microsatellite data was between South Africa and southern Australia
(pairwise FST = 0.037, [Phi]ST = 0.043) (Corrigan
et al. 2018). Clustering analysis showed only minor differences in
allele frequencies across regions and little evidence of population
structure (Corrigan et al. 2018). Overall, the authors conclude that
although spatial partitioning exists, the shortfin mako shark is
genetically homogenous at a large geographic scale. Taken together,
results of genetic analyses suggest that female shortfin mako sharks
exhibit fidelity to ocean basins, possibly to utilize familiar pupping
and rearing grounds, while males move across the world's oceans and
mate with females from various basins, thereby homogenizing genetic
variability (Heist et al. 1996; Schrey and Heist 2003; Taguchi et al.
2011; Corrigan et al. 2018).
Haplotype diversity in shortfin mako sharks has been found to be
high in several studies. Heist et al. (1996) found 25 haplotypes among
120 individuals for an overall haplotype diversity of 0.755 and a
nucleotide diversity of 0.347. Taguchi et al. (2011) found haplotype
and nucleotide diversity to be 0.92 and 0.0070, respectively, across
the global range of the species. Corrigan et al. (2018) detected 48
unique haplotypes among 365 individuals for a haplotype diversity of
0.894 0.013 and found very low nucleotide diversity of
0.004 0.003.
[[Page 68241]]
Demography
Natural mortality for shortfin mako sharks is low and was estimated
by Bishop et al. (2006) at 0.14 and 0.15 year-\1\ for males
and females, respectively. Chang and Liu (2009) calculated natural
mortality at 0.077-0.244 year-\1\ for females and 0.091-
0.203 year-\1\ for males in the Northwest Pacific. In the
North Atlantic, natural mortality was estimated at 0.101
year-\1\ (Bowlby et al. 2021). The generation time is
estimated at 25 years (Cort[eacute]s et al. 2015; Rigby et al. 2019).
In an analysis of productivity and susceptibility to longline
fisheries in the Indian Ocean, Murua et al. (2018) calculated a
population finite growth rate ([lambda]) for shortfin mako sharks of
1.049 year-\1\ (1.036-1.061; Murua et al. 2018). Liu et al.
(2015) estimated values for [lambda] of shortfin mako sharks off
California to be 1.1213 0.0635 year-\1\ and
1.0300 0.0763 year-\1\ for those in the
Northwest Pacific. As the species displays sexual dimorphism in size,
growth rates, and size at maturity, Tsai et al. (2015) argue that the
use of a two-sex demographic model more accurately estimates the
probability of decline risk and, therefore, better informs management
decisions. Further, as the mating mechanism of shortfin mako sharks
affects the proportion of breeding females and has not been
conclusively established, these scenarios (monogamous, polyandrous,
polygynous) should be modeled as well (Tsai et al. 2015). The authors
report that in the Northwest Pacific, without fisheries-related
mortality, values for [lambda] were 1.047, 1.010, and 1.075
year-\1\ for females and 1.056, 1.011, and 1.090
year-\1\ for males in monogamous, polyandrous, and
polygynous mating scenarios, respectively. Under fishing conditions at
the time of the study, all values for [lambda] dropped to less than one
(0.943, 0.930, and 0.955 year-\1\ for females and 0.918,
0.892, and 0.939 year-\1\ for males in monogamous,
polyandrous, and polygynous mating scenarios, respectively). Thus,
population declines were expected regardless of the mating system
modeled.
Productivity for the shortfin mako shark is quite low. In a recent
analysis using six methods, Cort[eacute]s (2016) determined that the
intrinsic rate of population increase (rmax) for Atlantic
shortfin mako sharks ranged from 0.036-0.134 yr-\1\. These
values were among the lowest calculated from 65 populations and species
of sharks (Cort[eacute]s 2016).
Abundance and Trends
Currently, there is no estimate of the absolute global abundance of
the shortfin mako shark; however, based on the age-structured
assessments conducted by ICCAT (2017) and the ISC Shark Working Group
(2018), current abundance is estimated to be one million individuals in
the North Atlantic and eight million individuals in the North Pacific
(FAO 2019). Comprehensive analyses based on available regional stock
assessments and standardized catch-per-unit-effort (CPUE) data have
been used by the International Union for Conservation of Nature (IUCN)
to approximate trends for the species globally.
In the 2019 IUCN Red List assessment, Rigby et al. estimated a
global population trend using the following data sources: (1) the 2017
stock assessments conducted by ICCAT for the North and South Atlantic,
(2) the 2018 stock assessment conducted by the ISC Shark Working Group
for the North Pacific, (3) standardized CPUE data for the South Pacific
from Francis et al. (2014), and (4) a preliminary stock assessment in
the Indian Ocean by Brunel et al. (2018). Individual trends by region
are discussed below. Using Just Another Red List Assessment (JARA)
(Winker et al. 2018; Sherley et al. 2019), a Bayesian state-space tool
for trend analysis of abundance indices, Rigby et al. (2019) found that
the species is declining in all oceans other than the South Pacific,
where it is increasing, with the steepest population declines indicated
in the North and South Atlantic. Due to the unreliable stock assessment
in the South Atlantic (discussed further below), Rigby et al. (2019)
considered the North Atlantic stock assessment to be representative of
the South Atlantic for the trend analysis. However, this may have
inaccurately represented the extent of decline in the South Atlantic;
the North Atlantic has experienced the largest known degree of decline
across the species' range, and while there is some possibility that the
South Atlantic has a similar stock status, the 2017 stock assessment
does not support that conclusion, and accordingly, ICCAT has not taken
comparable regulatory action for the species in the South Atlantic. A
global trend was estimated by weighting each region's trend by the
relative size of each region. To standardize the time period over which
the trends were calculated, JARA projected forward the amount of years
without observations that it would take to reach three generation
lengths. The overall median population reduction was estimated at 46.6
percent, with the highest probability of 50-79 percent reduction over
three generation lengths (72-75 years). Because available datasets for
each region cover different time periods and have different durations,
the timeframe of this trend is not a comparison between two specific
years, but rather a standardized timeframe of three generation lengths.
Trends indicated by Rigby et al. (2019) do not always align with
abundance and trend indicators from other sources, as discussed below.
The JARA framework used by Rigby et al. (2019) has been described as
inappropriate for this long-lived, sexually dimorphic species because
it only uses mean annual trends in the population over the assessment
period and does not consider size or age structures of the population
over recent decades (Kai 2021a). Available information on abundance and
trends by region is discussed below. Stock assessments provide
information on the status of a stock, with results presented using the
terms ``overfished'' and ``overfishing.'' Specific to the context of
the Magnuson-Stevens Fishery Conservation and Management Act (MSA), a
stock or stock complex is considered ``overfished'' when its biomass
has declined below minimum stock size threshold (MSST), defined as the
level of biomass below which the capacity of the stock or stock complex
to produce maximum sustainable yield (MSY) on a continuing basis has
been jeopardized (50 CFR 600.310(e)(2)(E)-(F)). Overfishing occurs
whenever a stock or stock complex is subjected to a level of fishing
mortality or total catch that jeopardizes the capacity of a stock or
stock complex to produce MSY on a continuing basis (50 CFR
600.310(e)(2)(B)). While the stock assessments referenced in this
finding do not define ``overfished'' and ``overfishing'' using the
exact language above, they use the two terms with equivalent meanings.
It is important to note that the terms ``overfished'' and
``overfishing'' do not have any specific relationship to the terms
``threatened'' or ``endangered'' as defined in the ESA. While a stock
that is overfished is not able to sustain an exploitive fishery at MSY
(i.e., the highest possible annual catch that can be sustained over
time), there is a significant difference between a stock that is
overfished and a stock that is in danger of extinction. A stock will
become overfished long before it is threatened with extinction, and can
be stable at biomass levels that do not support MSY. Similarly, one
goal of the MSA (and fisheries management organizations) is to
``rebuild'' overfished
[[Page 68242]]
stocks to biomass levels that will support MSY. This level can be
significantly above the biomass levels necessary to ensure that a
species is not in danger of extinction. Thus, evidence of declining
abundance that threatens the ability of the fishery to provide MSY are
relevant, but not dispositive of a threatened or endangered species
determination. Therefore, while available information about whether
specific stocks are overfished or experiencing overfishing is relevant
to and considered in our ESA extinction risk analysis, the fact that a
stock may be considered ``overfished'' or experiencing ``overfishing''
does not automatically indicate that any particular status is
appropriate under the ESA. Stock assessments, which provide information
for determining the sustainability of a fishery, are based on different
criteria than status reviews conducted under the ESA, which provide
information to assess the likelihood of extinction of the species. When
conducting a status review under the ESA, we use relevant information
from available stock assessments, such as levels of biomass and fishing
mortality, and apply the ESA's definitions of threatened and endangered
species to the information in the record using our standard tools of
ESA extinction risk analysis. As part of our ESA extinction risk
analysis, when examining whether overutilization for commercial
purposes is a threat to the species, we consider whether the species
has been or is being harvested at levels that contribute to or pose a
risk of extinction to the species.
North Atlantic Ocean
The most recent stock assessment by ICCAT indicates a combined 90
percent probability that the North Atlantic stock is in an overfished
state and is experiencing overfishing (ICCAT 2017). The nine model runs
used in this assessment generally agreed, indicating that stock
abundance in 2015 was below biomass at maximum sustainable yield
(BMSY) (ICCAT 2017). The age-structured stock assessment
model estimates historical declines in spawning stock fecundity (SSF,
defined as the number of pups produced in each year) from 1950
(unfished condition) to 2015 at 50 percent and recent declines (from
2006 to 2015) at 32 percent (FAO 2019). All assessment models were
consistent, and together indicated that the North Atlantic shortfin
mako shark has experienced historical declines in total biomass of
between 47-60 percent, and recent declines in total biomass of between
23-32 percent (FAO 2019). Projections conducted in the 2017 assessment
using a production model estimated that for a total allowable catch
(TAC; in this case, TAC refers to all sources of mortality and is not
limited to landings data) of 1,000 metric tons (t), the probability of
the stock being rebuilt and not experiencing overfishing (biomass (B) >
B MSY, and fishing mortality (F) < fishing mortality at MSY
(FMSY)) was only 25 percent by 2040 (one generation length).
In 2019, the ICCAT Standing Committee on Research and Statistics
(SCRS) carried out new projections for North Atlantic shortfin mako
shark through 2070 (two generation lengths) using an integrated model
(Stock Synthesis) at the Commission's request. The 2019 update to the
stock assessment projects that even with a zero TAC, the North Atlantic
stock would have a 53 percent probability of being rebuilt (SSF >
SSFMSY) and not experiencing overfishing (F <
FMSY) by 2045, and that regardless of TAC (including a TAC
of 0 t), the stock will continue declining until 2035 (ICCAT 2019).
Projections showed that a TAC of 500 t has a 52 percent probability of
rebuilding the stock, with overfishing not occurring, by 2070. The
projections indicated that realized TAC must be 300 t or less to ensure
that the stock will be rebuilt and not experiencing overfishing with at
least a 60 percent probability by 2070 (ICCAT 2019). These TAC options
with associated time frames and probabilities of rebuilding were
presented to the Commission; however, given the vulnerable biological
characteristics of this stock and these pessimistic projections, to
accelerate the rate of recovery and to increase the probability of
success, the SCRS recommended that the Commission adopt a non-retention
policy without exception.
The 2017 stock assessment and 2019 update to the stock assessment
present more accurate and rigorous results than the prior 2012
assessment. The 2012 assessment overestimated stock size,
underestimated fishing mortality, and suggested a low probability of
overfishing (ICCAT 2019). Input data and model structure changed
significantly between the 2012 and 2017 ICCAT stock assessments: catch
time series start earlier (1950 vs. 1971 in the 2012 assessment), some
biological inputs have changed and are sex-specific in the 2017
assessment, and additional length composition data became available
(ICCAT 2017). In addition, the CPUE series have been decreasing since
2010, which was the last year in the 2012 assessment models (ICCAT
2017). Finally, the age-structured model in the 2017 stock assessment
more accurately captured the time-lags in population dynamics of a
long-lived species than the production models used in 2012.
The IUCN's JARA trend analysis for the North Atlantic region relied
on the 2017 ICCAT stock assessment. Trend analysis of modeled biomass
estimated a median decline of 60 percent in the North Atlantic based on
annual rates of decline of 1.2 percent between 1950 and 2017 (Rigby et
al. 2019), which is consistent with the decrease in total biomass (60
percent) obtained from Stock Synthesis model run 3 from the 2017 ICCAT
stock assessment.
There is no stock assessment available for shortfin mako sharks in
the Mediterranean Sea. Ferretti et al. (2008) compiled data from public
and private archives representing sightings, commercial fisheries, and
recreational fisheries data in the western Mediterranean Sea and used
generalized linear models to conduct a meta-analysis of encounter
trends. Long-term combined trends for shortfin mako shark and porbeagle
(Lamna nasus) in the Mediterranean Sea indicate up to a 99.99 percent
decrease in abundance and biomass since the early 19th century, though
there was considerable variability among datasets due to geography and
sample size (Ferretti et al. 2008). While shortfin mako sharks spanning
a broad range of sizes (suggesting breeding/pupping in the region) are
occasionally reported as bycatch in swordfish and albacore longline
fisheries (Megalofonou et al. 2005), or in other artisanal or
commercial fisheries (Kabasakal 2015), from the eastern Mediterranean
Sea, no reliable estimates of abundance are available for this region.
Overall, the best available scientific and commercial information
indicates that the North Atlantic shortfin mako shark population has
experienced historical declines in biomass of between 47 and 60
percent, and declines will continue until at least 2035 regardless of
fishing mortality.
South Atlantic Ocean
Results of the most recent ICCAT stock assessment for shortfin mako
sharks in the South Atlantic indicate a high degree of uncertainty
(ICCAT 2017). One model (Just Another Gibbs Sampler emulating the
Bayesian production model) estimated that the stock was not overfished
(B2015/BMSY = 1.69-1.75) but that overfishing may
be occurring (F2015/FMSY = 0.86-1.07). Two runs
from this model indicate a 0.3-1.4 percent probability of the stock
being overfished and overfishing occurring, and a 29-47.4 percent
probability of the stock not being overfished but
[[Page 68243]]
overfishing occurring, or, alternatively, the stock being overfished
but overfishing not occurring, and a 52.3-69.6 percent probability of
the stock not being overfished and overfishing not occurring (ICCAT
2017). The Just Another Bayesian Biomass Assessment (JABBA) model
results indicated an implausible stock trajectory and were, therefore,
not relied upon for management advice. The Catch-only Monte-Carlo
method (CMSY) model estimates indicate that the stock could be
overfished (B2015/BMSY = 0.65 to 1.12) and that
overfishing is likely occurring (F2015/FMSY =
1.02 to 3.67). Considering catch scenarios C1 (catches starting in 1950
in the north and 1971 in the south, as reported in the March 2017 ICCAT
shortfin mako data preparatory meeting) and C2 (alternative estimated
catch series based on ratios (method described by Coelho and Rosa
2017), starting in 1971), Catch-only Monte-Carlo method model estimates
indicated a 23-89 percent probability of the stock being overfished and
overfishing occurring, a 11-48 percent probability of the stock not
being overfished but overfishing occurring, or alternatively, the stock
being overfished but overfishing not occurring, and only a 0-29 percent
probability of the stock not being overfished and overfishing not
occurring. Generally, while CPUE exhibited an increasing trend over the
last 15 years, both catches and effort increased contrary to the
expectation that the population is expected to decline with increasing
catch (FAO 2019). This inconsistency caused the ICCAT working group to
consider the assessment highly uncertain, and they conducted no
projections for the South Atlantic stock. Nevertheless, the combined
assessment models found a 19 percent probability that the stock is
overfished and is experiencing overfishing, a 48 percent probability of
the stock not being overfished but overfishing occurring, or
alternatively, the stock being overfished but overfishing not
occurring, and a 36 percent probability that the stock is not being
overfished or experiencing overfishing (ICCAT 2017). The assessment
also notes that, despite uncertainty, in recent years the stock may
have been at, or is already below, BMSY, and fishing
mortality is already exceeding FMSY. Based on the
uncertainty of the stock status, combined with the species' low
productivity, the ICCAT working group concluded that catches should not
increase above average catch for the previous 5 years, about 2,900 t
(ICCAT 2017; FAO 2019). There is a significant risk that the South
Atlantic stock could follow a trend similar to that of the North
Atlantic stock given that fishery development in the South Atlantic
predictably follows that in the North, and that the biological
characteristics of the stock are similar. The 2019 update to the stock
assessment (ICCAT 2019) therefore reiterates the recommendation that,
at a minimum, catch levels should not exceed the minimum catch in the
last 5 years of the assessment (2,001 t with catch scenario C1).
In addition to the ICCAT stock assessment, standardized catch rates
in South Atlantic longlines indicate steep declines in the average CPUE
of shortfin mako shark between 1979-1997 and 2007-2012 (Barreto et al.
2016). However, the methodologies used in this study have several
caveats and limitations, including the standardization analysis being
applied individually to each of the time series and the use of
different variables. Therefore, the results are not directly comparable
between the different time periods and cannot be used to infer the
total extent of decline over the entirety of the time series (FAO
2019).
Overall, despite high uncertainty in abundance and trends for the
species in this region, the best available scientific and commercial
data indicate that there is a 19 percent probability that the
population is overfished and is experiencing overfishing, and in recent
years the stock may have been at, or is already below, BMSY
and fishing mortality is already exceeding FMSY.
North Pacific Ocean
The most comprehensive information on trends for shortfin mako
sharks in the North Pacific comes from the 2018 ISC Shark Working Group
stock assessment, which found that the North Pacific stock was likely
not in an overfished condition and was likely not experiencing
overfishing between 1975 and 2016 (42 years) (ISC Shark Working Group
2018). This analysis used a Stock Synthesis model that incorporated
size- and age-specific biological parameters and utilized annual catch
data from 18 fleets between 1975 and 2016, annual abundance indices
from five fleets for the same period, and annual size composition data
from 11 fleets between 1994 and 2016 (Kai 2021a). This assessment
determined that the abundance of mature females was 860,200 in 2016,
which was estimated to be 36 percent higher than the number of mature
females at maximum sustainable yield (MSY) (ISC Shark Working Group
2018). Future projections indicated that spawning abundances were
expected to increase gradually over a 10-year period (2017-2026) if
fishing mortality remains constant or is moderately decreased relative
to 2013-2015 levels (ISC Shark Working Group 2018). Using results from
the ISC stock assessment, historical decline in abundance (1975-1985 to
2006-2016) is estimated at 16.4 percent, and a recent increase (2006-
2016) is estimated at 1.8 percent (CITES 2019).
The IUCN Red List Assessment for global shortfin mako shark also
used the ISC assessment to model the average trend in the North Pacific
stock over three generation lengths (72 years) and indicated a median
decline of 36.5 percent based on annual rates of decline of 0.6 percent
from 1975-2016 (Rigby et al. 2019). A comprehensive comparison of the
assessments by the ISC and the IUCN (Kai 2021a) describes JARA (applied
by Rigby et al. 2019) as a useful tool in extinction risk assessments
for data-poor pelagic sharks, but inappropriate for the relatively
data-rich North Pacific shortfin mako shark. The assessment by IUCN
used only the mean annual trends in the population over the assessment
period estimated from Stock Synthesis, and did not consider size or age
structure of the population over recent decades. Kai (2021a) concludes
that the results of the ISC's assessment of current and future status
of North Pacific shortfin mako shark are more robust and reliable than
those of the IUCN, and finds a median decline of the population
trajectory of 12.1 percent over three generation lengths with low
uncertainty.
The ISC Shark Working Group's 2021 indicator-based analysis for
shortfin mako sharks in the North Pacific used time series of catch,
indices of relative abundance (CPUE), and length-frequency data from
multiple fisheries over the time period 1957-2019 to monitor for
potential changes in stock abundance since the 2018 benchmark
assessment. Catch of shortfin mako shark in 2019 was the second highest
value for the last decade, and the scaled CPUEs indicated a stable and
slightly increasing trend in the four major fleets (U.S. Hawaii
longline shallow-set, Taiwan longline large-scale, Japan research and
training vessels, and Mexico observer for longline) (ISC Shark Working
Group 2021). The Working Group concluded that there were no signs of
major shifts in the tracked indicators that would suggest a revision to
the current stock assessment schedule for shortfin mako shark is
necessary (ISC Shark Working Group 2021). The next stock assessment is
scheduled for 2024.
[[Page 68244]]
Observer data from the Western and Central Pacific Fisheries
Commission (WCPFC) indicate that longline catch rates of mako sharks in
the North Pacific declined significantly by an average of 7 percent (95
percent confidence interval (CI): 3-11 percent) annually between 1995
and 2010 (Clarke et al. 2013). However, these data represent trends for
both longfin and shortfin mako sharks combined, and the performance of
the standardization model was poorer than for other studied shark
species, making the estimated trend less reliable. There were also
variable size trends for mako sharks in the North Pacific, with females
showing significant increases in median length in one region (Clarke et
al. 2013). In an updated indicator analysis using the same data, Rice
et al. (2015) noted that the standardized CPUE trend looked relatively
stable between 2000 and 2010, but no inference was possible for the
last 4 years (2010-2014) due to data deficiencies in some years.
Kai et al. (2017) analyzed catch rates in the Japanese shallow-set
longline fishery in the western and central North Pacific from 2006-
2014, finding an increasing trend since 2008. However, fishery-
independent logbook data collected from Japanese research and training
vessels in the western and central North Pacific (mainly 0-40[deg] N
and 130[deg] E-140[deg] W) from 1992-2016 showed a decreasing catch
rate since 2008 (Kai 2019). The opposing trends indicated by fishery-
dependent and -independent data in this region may be due to factors
such as differing areas of operation, differing gear types,
underreporting by both data sources, and differing model structures
applied to the data (Kai 2019). Additionally, standardized CPUE
estimates from 2011-2019 in the Japanese longline fleet operating in
the North Pacific Ocean showed a stable trend from 2011 to 2016, with a
slight decline after 2016 (Kanaiwa et al. 2021). The authors note that
observer coverage in the fleet is low (1.7-3.0 percent in certain
areas) and that these results may not represent the overall trend for
the North Pacific stock of shortfin mako shark (Kanaiwa et al. 2021).
Results from stock assessments and standardized CPUE trends from
observer data are more comprehensive, robust, and reliable than trends
from fishery logbook data. Therefore, we find that the best scientific
and commercial information available indicates that shortfin mako
sharks in the North Pacific are neither overfished nor experiencing
overfishing, and the population is likely stable and potentially
increasing despite evidence of historical decline and indications of
recent decline in fishery-independent datasets.
South Pacific Ocean
In the South Pacific, longline catch rates reported to WCPFC did
not indicate a significant trend in abundance of mako shark (shortfin
and longfin combined) between 1995 and 2010 (Clarke et al. 2013). In an
updated indicator analysis, standardized CPUEs for the mako shark
complex show a relatively stable trend in relative abundance, with low
points in 2002 and 2014, though the 2014 point is based on relatively
few data and should be interpreted with caution (Rice et al. 2015). In
New Zealand waters, logbook and observer data from 1995-2013 analyzed
by Francis et al. (2014) indicate that shortfin mako sharks were not
declining, and may have been increasing, over the period from 2005-
2013. More recently, an analysis of the data did not result in
statistically significant trend fits for two of the data series; those
that were significant were increasing (Japanese South 2006-2015,
Domestic North 2006-2013, and Observer Data 2004-2013) (FAO 2019).
Trend analysis of modeled biomass indicates a median increase of 35.2
percent over three generation lengths based on estimated annual rates
of increase of 0.5 percent from 1995-2013 (Rigby et al. 2019). In sum,
the best scientific and commercial information available indicates that
shortfin mako sharks in the South Pacific have an increasing population
trend.
Indian Ocean
Only preliminary stock assessments using data-limited assessment
methods have been conducted for the shortfin mako shark in the Indian
Ocean, with few other stock indicators available. Catch data are
thought to be incomplete for several reasons: landings do not reflect
the number of individuals finned and discarded at sea, shortfin mako
sharks are not sufficiently specified in catch data and are often
aggregated with other species, shortfin mako shark may be misidentified
as longfin mako shark, and recorded weight may often refer to processed
weight rather than live weight (Bonhommeau et al. 2020). These factors
were a significant consideration in our evaluation of the species. With
these caveats in mind, a preliminary assessment by Brunel et al. (2018)
was carried out based on CPUE estimates from Portuguese (2000-2016) and
Spanish (2006-2016) swordfish and tuna longline fleets operating in the
Indian Ocean Tuna Commission (IOTC) Convention area. Results from two
models (a Bayesian Schaefer-type production model and another model
analyzing the trends of catches) indicate that the stock is
experiencing overfishing (F2015/FMSY = 2.57), but
is not yet overfished (B2015/BMSY close to one)
(Brunel et al. 2018). However, there were considerable uncertainties in
the estimates and conflicting trends in biomass between the two models
used. Nonetheless, trajectories showed consistent trends toward both
overfished and subject to overfishing status (Brunel et al. 2018).
Using the results of the Schaefer model from Brunel et al. (2018),
historical decline (1970-1980 to 2005-2015) was estimated at 26
percent, recent decline (2005 to 2015) was estimated at 18.8 percent,
and future 10-year decline was projected at 41.6 percent from the
historical baseline (1970-1980 to 2015-2025) (CITES 2019). A trend
analysis for modeled biomass in the Indian Ocean using Brunel et al.'s
assessment indicates a median decline of 47.9 percent over three
generation lengths based on annual rates of decline of 0.9 percent from
1971-2015 (Rigby et al. 2019).
A more recent preliminary assessment using updated catch and CPUE
indices also indicates that the shortfin mako shark in the Indian Ocean
is experiencing overfishing but is not overfished (Bonhommeau et al.
2020). This assessment uses nominal catch of shortfin mako shark as
reported to the IOTC (1964-2018) and scaled CPUEs from Japan (1993-
2018), Spain (2001-2018), Taiwan (2005-2018), and Portugal (2000-2018).
Bonhommeau et al. (2020) used JABBA and CMSY models, both of which gave
results that were generally consistent with the previous assessment:
that the stock is currently undergoing overfishing and is not
overfished.
In a separate study, Wu et al. (2021) analyzed standardized CPUE
trends using observer records and logbook data from 2005-2018 for the
Taiwanese longline fishery in the Indian Ocean, which was the second
largest shortfin mako shark-catching nation in the region in 2019. The
standardized CPUEs indicate a gradual decrease between 2005 and 2007,
followed by a sharp increase in 2008, a slow decline between 2008 and
2015, and another increase between 2015 and 2018 (Wu et al. 2021).
However, Wu et al. (2021) note that the rapid increases in CPUEs
between 2007 and 2008 and later between 2015 and 2017 may be
unrealistic for the stock biomass of such a long-lived species, and
suggest that the results may be due to increased reporting by skippers
and observers.
[[Page 68245]]
Logbook data from Japanese longliners operating in the Indian Ocean
from 1993-2018 indicate that abundance of shortfin mako shark decreased
from 1993-2009, and increased slightly since then (Kai and Semba 2019).
Standardized CPUE has risen after 2008 in Portuguese and Spanish
longline fleets as well (Coelho et al. 2020; Ramos-Cartelle et al.
2020), although these data sets were included in the preliminary stock
assessment conducted by Bonhommeau et al. (2020). In the Arabian Sea
CPUE data suggest variable abundance and little evidence of significant
population reduction (Jabado et al. 2017). Fishing pressure in this
region is high, and because the species has high susceptibility to
pelagic fisheries, Jabado et al. (2017) estimated that over the past 3
generations the population has declined 20-30 percent, with future
declines expected over the next 3 generations. Results from these
studies may reflect partial stock status in the Indian Ocean, but may
not have sufficient spatial coverage to be indicative of the entire
stock status.
In sum, the best available scientific and commercial information
indicates that shortfin mako shark population in the Indian Ocean is
experiencing overfishing but is not yet overfished, and recent
increasing CPUE trends are indicated in Spanish, Portuguese, and
Taiwanese longline fleets. Catch data have the potential to be
substantially underestimated and the recent increases in CPUE from
these fleets may not reflect trends in abundance.
Summary
Overall, while abundance estimates for the shortfin mako shark are
not available for all regions, the stock assessments available for the
North Atlantic and North Pacific Oceans indicate current numbers of
about one million and eight million individuals, respectively (FAO
2019). These estimates were generated by the FAO Expert Advisory Panel,
which extracted these numbers using the age-structured assessments
conducted by ICCAT (2017) and the ICS Shark Working Group (2018). Rigby
et al. (2019) conducted a trend analysis of shortfin mako shark
abundance indices using the 2017 ICCAT stock assessment in the
Atlantic, the 2018 ISC Shark Working Group stock assessment in the
North Pacific, a preliminary stock assessment for the Indian Ocean
(Brunel et al. 2018), and a CPUE indicator analysis from New Zealand
for the South Pacific (Francis et al. 2014). Due to the unreliable
stock assessment in the South Atlantic, Rigby et al. (2019) considered
the North Atlantic stock assessment to be representative of the South
Atlantic for the trend analysis. However, this may have inaccurately
represented the extent of decline in the South Atlantic for reasons
described above. This assessment estimates the overall median
population reduction for the global shortfin mako shark population at
46.6 percent, with the highest probability of 50-79 percent reduction
over three generation lengths (72-75 years) (Rigby et al. 2019),
although the JARA framework used by Rigby et al. has been described as
inappropriate for this species as it only uses mean annual trends in
the population over the assessment period and does not consider size or
age structure of the population over recent decades (Kai 2021a).
Population decline has been indicated in the North Atlantic with
high certainty, and abundance is likely to continue declining until at
least 2035 even in the absence of fishing mortality (ICCAT 2019). In
the North Pacific, while there is evidence of historical decline,
recent assessments indicate that the stock is neither overfished nor
experiencing overfishing, and the population is likely stable or
potentially increasing (ISC Shark Working Group 2018). Although a stock
assessment has not been completed for shortfin mako sharks in the South
Pacific, the best available scientific and commercial data and analyses
indicate an increasing population trend (Francis et al. 2014; Rigby et
al. 2019). Abundance of the shortfin mako shark in the South Atlantic
and Indian Oceans is not as clear, given significant uncertainties in
the data available from these regions. The most recent stock
assessments of shortfin mako sharks in the South Atlantic has a high
degree of uncertainty, and indicate a combined 19 percent probability
that the stock is overfished and experiencing overfishing (ICCAT 2017).
Preliminary assessments in the Indian Ocean indicate that the
population is experiencing overfishing but is not yet overfished
(Brunel et al. 2018; Bonhommeau et al. 2020).
Extinction Risk Analysis
In evaluating the level of risk faced by a species and deciding
whether the species is threatened or endangered, we must consider all
relevant data and are required under the ESA to base our conclusions on
the best scientific and commercial data available. In evaluating and
interpreting the best available data we also apply professional
judgment. We evaluate both the viability of the species based on its
demographic characteristics (abundance, productivity, spatial
distribution, and diversity; see McElhany et al. (2000)), and the
threats to the species as specified in ESA section 4(a)(1)(A)-(E).
Methods
This section discusses the methods used to evaluate threats and the
overall extinction risk to the shortfin mako shark. For purposes of the
risk assessment, an ERA Team comprising biologists and shark experts
was convened to review the best available information on the species
and evaluate the overall risk of extinction facing the shortfin mako
shark, now and in the foreseeable future.
According to regulations implementing section 4 of the ESA that
were in place during the ERA Team's deliberations, which was consistent
with our practice since 2009 in accordance with a legal opinion of the
Solicitor of the United States Department of the Interior, ``The
Meaning of `Foreseeable Future' in section 3(20) of the Endangered
Species Act'' (M-37021, Jan. 16, 2009; referred to herein as ``the 2009
M-Opinion''), the foreseeable future extends only so far into the
future as we can reasonably determine that both the future threats and
the species' responses to those threats are likely. See 50 CFR
424.11(d). Under our longstanding practice we describe the foreseeable
future on a case-by-case basis, using the best available data and
taking into account considerations such as the species' life-history
characteristics, threat-projection timeframes, and environmental
variability. In addition, because a species may be susceptible to a
variety of threats for which different data are available, or which
operate across different time scales, the foreseeable future may not
necessarily be reducible to a particular number of years and may not be
defined the same way for each threat. Although the regulations were
vacated and remanded without a decision on the merits on July 5, 2022,
by the United States District Court for the Northern District of
California, and that order has been temporarily stayed as of September
21, 2022, whether or not those regulations remain in place does not
affect our understanding or application of the ``foreseeable future.''
The 2019 regulations merely codified the approach of our longstanding
interpretation of this term in use prior to the issuance of these
regulations (see 84 FR 45020, August 27, 2019), and the court did not
make any findings on the merits that would call this approach into
question. Thus, with or without the 2019 regulations, we would continue
to apply an approach to the foreseeable future rooted in the 2009 M-
Opinion.
[[Page 68246]]
In determining an appropriate foreseeable future timeframe for the
shortfin mako shark, the ERA Team first considered the species' life
history. The species matures late in life, with females estimated to
mature at an age of 15-21 years and males at 6-9 years of age (Bishop
et al. 2006; Natanson et al. 2006; Semba et al. 2009; Groeneveld et al.
2014). The species has high longevity of at least 28-32 years (Bishop
et al. 2006; Natanson et al. 2006) and exhibits relatively slow growth
rates and low productivity (Cort[eacute]s et al. 2015). The ERA Team
also considered generation time for the shortfin mako shark, which is
defined as the average interval between the birth of an individual and
the birth of its offspring, and has been estimated at 25 years
(Cort[eacute]s et al. 2015). Given the life history characteristics of
the shortfin mako shark, the ERA Team concluded that it would likely
take several decades for any conservation management actions to be
realized and reflected in population abundance indices.
As the main threats to the species are overutilization in
commercial fisheries and the inadequacy of regulatory measures that
manage these fisheries (see Summary and Analysis of Section 4(a)(1)
Factors below), the ERA Team then considered the time period over which
they could reasonably predict the likely impact of these threats on the
biological status of the species. The ERA Team took available
projections for shortfin mako shark abundance into consideration: the
2019 ICCAT update to the stock assessment for the North Atlantic
carried out projections over 2 generation lengths, or 50 years; the ISC
Shark Working Group's 2018 stock assessment for North Pacific shortfin
mako sharks used 10-year projections; and the IUCN Red List Assessment
carried out projections based on available data to achieve a 3
generation length time frame using JARA.
In examining these projections and their respective confidence
intervals, the ERA Team noted that uncertainty increased substantially
after about one generation length in all cases across multiple regions
of the species' range. The ERA Team noted that in the IUCN JARA
projections conducted for shortfin mako sharks by region, uncertainty
(i.e., the difference between the median and confidence intervals)
increased to 50 percent by 2030 for the South Pacific population (about
18 years projected), and 40 percent by 2040 for the Indian and North
Pacific populations (about 25 years projected). Additionally, the ERA
Team noted that ICCAT's report of the 2019 shortfin mako shark stock
assessment update meeting emphasizes that the Kobe II Strategy Matrix
(K2SM) used to provide scientific advice for the North Atlantic stock
does not capture all uncertainties associated with the fishery and the
species' biology. Specifically, ICCAT's SCRS stated that ``the length
of the projection period (50 years) requested by the Commission
significantly increases the uncertainty of the results. Therefore, the
Group advised that the results of the K2SM should be interpreted with
caution,'' (ICCAT 2019). As a result of this statement, the ERA Team
considered the 50-year projection to have questionable scientific
merit, with estimates over that time frame only provided because the
Commission requested them. Given the concerns about uncertainty that
were repeatedly highlighted by the SCRS (ICCAT 2019), the ERA Team
concluded that the 50-year period was not an appropriate time period
for the foreseeable future.
In addition to uncertainty in projected abundance trends, the ERA
Team discussed the uncertainty associated with future management
measures and fishing behavior across regions. ICCAT is currently the
only major Regional Fishery Management Organization (RFMO) with
management measures specific to shortfin mako sharks, and recently
adopted a two-year retention ban for the species in the North Atlantic.
The conservation benefit of this measure is uncertain, however, as it
does not require fishermen to modify gear or fishing behavior that
would reduce at-vessel or post-release mortality of the species.
Further, management of the species after this two-year ban expires is
unknown. Some of the top shortfin mako shark-catching nations in this
region (Spain, Portugal, and Morocco) have very recently announced
unilateral retention prohibitions for North Atlantic shortfin mako
shark, although the effect these bans will have on the species is again
unknown, even if they ultimately are well implemented. Although
projections carried out in 2019 by ICCAT's SCRS indicate that the North
Atlantic stock will continue declining until approximately 2035
regardless of fishing mortality, the effect on stock status beyond this
varies greatly with fishing mortality levels. Beyond the North Atlantic
and North Pacific (where fishing data is also considered robust),
fishing harvest and, especially, at-vessel and post-release mortality
data are less thoroughly documented, introducing considerable
uncertainty in projections of fishery impacts past a few decades.
After considering the best available scientific and commercial
information on the shortfin mako shark's life history, projected
abundance trends, and current and future management measures and
fishing behaviors, the ERA Team concluded that a biologically
reasonable foreseeable future timeframe would be 25 years, or one
generation length, for the shortfin mako shark. Because the main
threats to the species are overutilization in commercial fisheries and
the inadequacy of existing regulatory mechanisms to prevent
overutilization in these fisheries, the ERA Team found that this
timeframe would allow for reliable predictions regarding the likely
impact of these threats on the future biological status of the species.
While we conclude that the ERA Team assembled the best scientific
and commercial information, it is the role of the agency rather than
the team to determine the appropriate application of the agency's
interpretations of key statutory terms and of agency policy to the
factual record, and to ultimately determine the species' listing status
under the ESA. Based on the best available scientific and commercial
information, we disagree with the ERA Team's conclusion that the
foreseeable future extends only 25 years, or one generation length, and
have determined that application of a 50-year time frame is more
appropriate in this case generally, though for some individual threats
our ability to predict the specific trends and the species' responses
is less robust than for others. We agree that fisheries mortality and
inadequate regulatory mechanisms to address this threat are, and will
continue to be, the main threats to the species. While we also agree
with the ERA Team's characterization of the shortfin mako shark's life
history, we find this information to indicate that it would take more
than one generation length for effects of conservation actions to be
reflected in abundance indices. During peer review of the Status Review
Report, reviewers noted that changes in threats and conservation
measures for shortfin mako sharks might take decades to become visible
in the mature population, and all three reviewers were of the opinion
that a longer time horizon would be appropriate. We find that the ERA
Team unnecessarily limited the length of the foreseeable future by
relying on statistical confidence levels for projected population
trends. The 2009 M-Opinion, which for over a decade has provided the
basis for NMFS's interpretation of this term, states that ``the
foreseeable future for a given species is not limited to the length of
time into the future for which a species' status can be quantitatively
[[Page 68247]]
modeled or predicted within predetermined limits of statistical
confidence; however, uncertainties of any modeling efforts should be
considered and documented.'' Although, as the ERA Team noted,
uncertainty in abundance projections increases with the length of
projections, we have determined that we can use available projections,
our knowledge of the species' life history, and predicted levels of
fishing mortality to inform what is likely to be the status of the
species in a given region over a longer timeframe. Also, although
changes in threats (i.e., fisheries removals) would be observable over
a 25-year period, we do not find that this time period is sufficient to
measure and understand the population-level response to these changes,
which would only be observable over a longer time period given the
species' late age-at-maturity (this was also noted by a reviewer during
the peer review process of the Status Review Report). A 50-year
timeframe would encompass the duration over which changes in
productivity would be expected to occur and be measurable while also
taking into account the considerable uncertainty in future management
measures and population trends as described by the ERA Team. To
conclude, we find that our knowledge of the species' life history and
of the fisheries impacting the species allow us to reasonably determine
the likely threats facing the species (overutilization for commercial
purposes and the related inadequacy of existing regulatory mechanisms)
and the species' likely response to these threats (reflected in
abundance trends and other demographic factors) over approximately 50
years, or two generation lengths. We therefore consider the foreseeable
future to extend 50 years (two generation lengths) rather than 25 years
as determined by the ERA Team.
The ability to measure or document risk factors to a marine species
is often limited, and quantitative estimates of abundance and life
history information are often lacking altogether. Therefore, in
assessing extinction risk of a species with limited data available from
certain regions, it is important to include both qualitative and
quantitative information. In assessing extinction risk to the shortfin
mako shark, the ERA Team considered the demographic viability factors
developed by McElhany et al. (2000) and the risk matrix approach
developed by Wainwright and Kope (1999) to organize and summarize
extinction risk considerations. The approach of considering demographic
risk factors to help frame the consideration of extinction risk has
been used in many of our status reviews (which can be accessed online
at http://www.nmfs.noaa.gov/pr/species). In this approach, the
collective condition of individual populations is considered at the
species level according to four demographic viability factors:
abundance, growth rate/productivity, spatial structure/connectivity,
and diversity. These viability factors reflect concepts that are well-
founded in conservation biology and that individually and collectively
provide strong indicators of extinction risk. To some extent these
factors reflect the impacts that the operative threats have already had
or are having on the species.
Using these concepts, the ERA Team evaluated demographic risks by
assigning a risk score to each of the four demographic risk factors.
The contribution of each demographic factor to extinction risk was
scored according to the following scale: 0--unknown risk, 1--low risk,
2--moderate risk, and 3--high risk. Detailed definitions of the risk
scores can be found in the Status Review Report. The scores were then
tallied and summarized for each demographic factor. The ERA Team
discussed the range of perspectives for each of the factors and the
supporting data upon which they were based. ERA Team members were then
given the opportunity to revise scores after the discussion if they
felt their initial analysis had missed any pertinent data discussed in
the group setting.
The ERA Team also performed a threats assessment for the shortfin
mako shark by evaluating each threat in terms of its contribution to
the extinction risk of the species. The contribution of each threat to
the species' extinction risk was scored on the following scale: 0--
unknown risk, 1--low risk, 2--moderate risk, and 3--high risk. The
scores were then tallied and summarized for each threat, and the ERA
Team again discussed the range of perspectives before providing final
scores. As part of the threats assessment, the ERA Team considered the
synergistic and combined effects of the threats acting together as well
as individually. It should be emphasized that the scoring exercise for
both demographic risks and threats was simply a tool to help the ERA
Team members organize the information and assist in their thought
processes for determining the overall risk of extinction for the
shortfin mako shark, and is a common and well-accepted feature of our
species assessments.
Guided by the results from the demographic risk analysis and the
threats assessment, the ERA Team members were asked to use their
informed professional judgment to make an overall extinction risk
determination for the shortfin mako shark. For this analysis, the ERA
Team considered three levels of extinction risk: 1--low risk, 2--
moderate risk, and 3--high risk. Detailed definitions of these risk
levels are as follows: 1 = Low risk: A species is at low risk of
extinction if it is not at a moderate or high level of extinction risk
(see ``Moderate risk'' and ``High risk'' below). A species may be at a
low risk of extinction if it is not facing threats that result in
declining trends in abundance, productivity, spatial structure, or
diversity. A species at low risk of extinction is likely to show stable
or increasing trends in abundance and productivity with connected,
diverse populations; 2 = Moderate risk: A species is at moderate risk
of extinction if it is on a trajectory that puts it at a high level of
extinction risk in the foreseeable future (50 years in this case) (see
description of ``High risk''). A species may be at moderate risk of
extinction due to projected threats or declining trends in abundance,
productivity, spatial structure, or diversity; 3 = High risk: A species
with a high risk of extinction is at or near a level of abundance,
productivity, spatial structure, and/or diversity that places its
continued persistence in question. The demographics of a species at
such a high level of risk may be highly uncertain and strongly
influenced by stochastic or depensatory processes. Similarly, a species
may be at high risk of extinction if it faces clear and present threats
(e.g., confinement to a small geographic area; imminent destruction,
modification, or curtailment of its habitat; or disease epidemic) that
are likely to create present and substantial demographic risks.
The ERA Team adopted the ``likelihood point'' method for ranking
the overall risk of extinction to allow individuals to express
uncertainty. Following this method, each ERA Team member distributed 10
``likelihood points'' across the three extinction risk levels,
representing the likelihood that the species falls into each risk
category. Each Team member had the ability to cast points in more than
one category to account for uncertainty, and the points that each Team
member allocated across the categories summed to 10. This method has
been used in previous NMFS status reviews (e.g., oceanic whitetip
shark, Pacific salmon, Southern Resident killer whale, Puget
[[Page 68248]]
Sound rockfish, Pacific herring, and black abalone) to structure the
ERA Team's thinking and express levels of uncertainty when assigning
risk categories. After scores were provided, the ERA Team discussed the
range of perspectives and the supporting data on which scores were
based, and members were given the opportunity to revise scores if
desired after the discussion. Likelihood points were then summed by
extinction risk category. Other descriptive statistics, such as mean,
variance, and standard deviation, were not calculated, as the ERA Team
concluded that these metrics would add artificial precision to the
results.
Finally, consistent with the appropriately limited role of the
Team, the ERA Team did not make ultimate recommendations as to whether
the species should be listed as threatened or endangered. Rather, the
ERA Team drew scientific conclusions about the overall risk of
extinction faced by the shortfin mako shark under present conditions
and in the foreseeable future based on an evaluation of the species'
demographic risks and assessment of threats.
Because we determined to adopt a different period of years as the
``foreseeable future'' for the shortfin mako shark after the ERA Team's
work concluded, we also present our own assessment of extinction risk
over the foreseeable future (50 years or two generation lengths) in a
later section of this document alongside the ERA Team's results.
Demographic Risk Analysis
Abundance
The ERA Team assessed available abundance and trend information by
region, including formal stock assessments, preliminary stock
assessments using data-limited assessment methods, and standardized
CPUE trends. There are no global abundance estimates available;
however, using the formal stock assessments available for the North
Atlantic and North Pacific, current abundance has been estimated at one
million and eight million individuals, respectively (FAO 2019). Using
the regional rates of change weighted by an area-based estimate of the
size of each region as a proportion of the species' global
distribution, the IUCN Red List assessment estimated global decline at
46.6 percent over three generation lengths, with the particular years
covered varying by region (Rigby et al. 2019). Although historical
declines of varying degrees are evident across all oceans, current
trends are mixed.
As discussed previously, the most recent stock assessment for
shortfin mako shark in the North Atlantic indicates a combined 90
percent probability that the stock is in an overfished state and is
experiencing overfishing (ICCAT 2017). The age-structured stock
assessment model estimates historical declines in SSF from 1950
(unfished condition) to 2015 at 50 percent, and recent declines (from
2006-2015) at 32 percent (ICCAT 2017, FAO 2019). All nine assessment
model runs were consistent, and together indicated that shortfin mako
sharks in the North Atlantic have experienced historical declines
(1950-2015) in total biomass of 47-60 percent, and recent declines
(2006-2015) in total biomass of 23-32 percent (ICCAT 2017, FAO 2019).
The 2019 update to the stock assessment projects that even with a zero
TAC, there is a 53 percent probability that the North Atlantic stock
will be rebuilt and not experiencing overfishing by 2045, and that
regardless of TAC (in this case, TAC refers to all sources of mortality
and is not limited to landings), the stock will continue declining
until 2035 (ICCAT 2019). Overall, the ERA Team agreed that the findings
from the stock assessment and projections were concerning. The ERA Team
discussed how to appropriately interpret the stock assessment's focus
on being rebuilt (SSF > SSFMSY) and without overfishing (F <
FMSY) in the context of assessing extinction risk. As
discussed previously in Abundance and Trends, while the fisheries
management goal of rebuilding an overfished stock relates to achieving
biomass levels that will allow for production of MSY, this can be
significantly above the biomass levels necessary to ensure that a
species is not in danger of extinction. While it will likely take
decades for the stock to meet these fisheries management criteria
(rebuilt and without overfishing), this does not indicate that the
stock is at risk of becoming extirpated now or over the foreseeable
future. Additionally, the ERA Team weighed the potential effects of the
recent two-year North Atlantic shortfin mako shark retention
prohibition on fishing mortality and abundance (ICCAT Recommendation
21-09, discussed in Inadequacy of Existing Regulatory Mechanisms below,
which entered into force on June 17, 2022). As data for each fishing
year is not reported until the following calendar year, the effect of
this measure on fishing mortality will not be easily assessed until
2024 when the landings and discard data from 2023 can be analyzed. As
noted above, the low productivity and slow population growth of
shortfin mako shark may also mean that measurable impacts of this
measure on abundance do not manifest for several years, when a new
cohort enters the fishery. The Team concluded that there was
significant uncertainty concerning both the effect of the measure and
the future management of the stock after the two-year time period, and
therefore did not significantly rely on any potential effect of the
measure when drawing conclusions about the stock's abundance or trends.
We agree with the ERA Team's assessment of abundance and related
considerations in the North Atlantic. We also recognize that without a
substantial reduction in total fishing mortality (annual TAC of 500 t
or less), it is unlikely that the stock will be rebuilt by 2070 (ICCAT
2019). Even if the spawning stock is not considered rebuilt by the
stock assessment metric (SSF > SSFMSY), this does not
necessarily mean that the stock will be in danger of being extirpated.
However, given that fishing mortality is still high in this region
(1,709 t in 2020) compared to even the greatest assessed TAC level
(1,100 t), this level of removal will lead to continued declines.
Unless aggressive management measures effectively reduce fishing
mortality in this region, declines will likely continue throughout the
foreseeable future (50 years). ICCAT has a demonstrated track record of
taking multilateral actions to address data gaps and to respond to
indications of declining stock status (see previous ICCAT measures
specific to the stock in Inadequacy of Existing Regulatory Mechanisms
below). The two-year retention prohibition adopted by ICCAT in 2021 is
the most recent step that has been taken to conserve and manage this
stock in line with the ICCAT Convention. ICCAT's track record would
indicate that similar or additional measures are likely to be continued
or taken, as needed, to ensure ICCAT's objectives of ending overfishing
and rebuilding the stock to levels that support MSY are met.
Recommendation 21-09 calls for the Commission to review the measure no
later than the annual meeting in 2024 to consider additional measures
to reduce total fishing mortality. Overall, we conclude that the best
available scientific and commercial data indicate that the stock is
overfished and experiencing overfishing, has experienced an estimated
50 percent decline in SSF from 1950 to 2015, and will continue
decreasing until 2035 regardless of TAC.
The 2017 stock assessment for shortfin mako sharks in the South
Atlantic indicated a high degree of
[[Page 68249]]
uncertainty. The combined assessment models found a 19 percent
probability that the population is overfished and is experiencing
overfishing (ICCAT 2017). The authors concluded that despite high
uncertainty, in recent years the South Atlantic stock may have been at,
or already below, BMSY and fishing mortality is likely
exceeding FMSY (ICCAT 2017). Projections for the stock were
not completed in 2019 due to high uncertainty. The ERA Team agreed that
the best available scientific and commercial data indicate some degree
of historical and ongoing population decline, but was unable to draw
conclusions about the degree of decline due to the highly uncertain
results of the 2017 stock assessment. We agree with the ERA Team's
assessment of abundance in the South Atlantic.
The most comprehensive information on trends for shortfin mako
sharks in the North Pacific comes from the 2018 ISC Shark Working Group
stock assessment, which found that the North Pacific stock was likely
not in an overfished condition and was likely not experiencing
overfishing between 1975 and 2016 (42 years) (ISC Shark Working Group
2018). This assessment determined that the abundance of mature females
was 860,200 in 2016, which was estimated to be 36 percent higher than
the number of mature females at MSY (ISC Shark Working Group 2018).
Future projections indicated that spawning abundance is expected to
increase gradually over a 10-year period (2017-2026) if fishing
mortality remains constant or is moderately decreased relative to 2013-
2015 levels (ISC Shark Working Group 2018). Using results from the ISC
stock assessment, historical decline in abundance (1975-1985 to 2006-
2016) is estimated at 16.4 percent, and a recent increase (2006-2016)
is estimated at 1.8 percent (CITES 2019). While the IUCN used the ISC
assessment to model the average trend in the North Pacific stock over
three generation lengths (72 years), resulting in a median decline of
36.5 percent (Rigby et al. 2019), Kai (2021a) found a median decline of
the population trajectory of 12.1 percent over three generation lengths
with low uncertainty. The ERA Team concluded that despite evidence of
historical decline, the best available scientific and commercial data
indicate that shortfin mako sharks in the North Pacific are neither
overfished nor experiencing overfishing, and the population is likely
stable and potentially increasing. We agree with the ERA Team's
conclusion.
Although a stock assessment is not available for shortfin mako
sharks in the South Pacific, available information indicates that the
population is increasing. Standardized CPUEs for the mako shark complex
(i.e., both shortfin and longfin mako shark) show a relatively stable
trend in relative abundance, with low points in 2002 and 2014, though
the 2014 point is based on relatively few data and should be
interpreted with caution (Rice et al. 2015). In New Zealand waters,
logbook and observer data from 1995-2013 analyzed by Francis et al.
(2014) indicate that shortfin mako sharks were not declining, and may
be increasing, over the period from 2005-2013. More recently, trend
estimations using data from these two studies (Francis et al. 2014 and
Rice et al. 2015) did not result in statistically significant trend
fits for two of the data series; those that were significant were
increasing (Japanese South 2006-2015, Domestic North 2006-2013, and
Observer Data 2004-2013) (FAO 2019). Trend analysis of modeled biomass
indicates a median increase of 35.2 percent over three generation
lengths (Rigby et al. 2019). In sum, the ERA Team agreed that the best
available scientific and commercial data for shortfin mako sharks in
the South Pacific indicate an increasing population trend, and we agree
with the ERA Team's conclusion.
Finally, in the Indian Ocean, preliminary stock assessments using
data-limited assessment methods are available for shortfin mako sharks
and indicate that the stock is experiencing overfishing, but is not yet
overfished (Brunel et al. 2018; Bonhommeau et al. 2020). This means
that while the stock is subjected to a level of fishing mortality that
jeopardizes the stock's ability to produce MSY, biomass levels are
still high enough that the stock is able to produce MSY on a continuing
basis. Both preliminary assessments are considered highly uncertain due
to limitations in catch data. Using the results of the Schaefer model
from Brunel et al. (2018), historical decline (1970-1980 to 2005-2015)
was estimated at 26 percent, recent decline (2005 to 2015) was
estimated at 18.8 percent, and future 10-year decline was projected at
41.6 percent from the historic baseline (1970-1980 to 2015-2025) (CITES
2019). A trend analysis for modeled biomass in the Indian Ocean using
Brunel et al.'s assessment indicates a median decline of 47.9 percent
over three generation lengths (Rigby et al. 2019). Recent increases in
CPUE trends are indicated in Spanish, Portuguese, and Taiwanese
longline fleets (Coelho et al. 2020; Ramos-Cartelle et al. 2020; Wu et
al. 2021), though it should be noted that these datasets were included
in the assessment by Bonhommeau et al. (2020). Overall, the ERA Team
concluded that the best available scientific and commercial data
indicate some level of historical population decline and indicate that
shortfin mako sharks are currently experiencing overfishing in this
region. We agree with the ERA Team's conclusion.
The ERA Team considered the risk associated with abundance of the
global species using the best available scientific and commercial
information, summarized above. Reported landings represent a
substantial underestimate of mortality resulting from fisheries
interactions because they do not fully account for mortalities that
result from fisheries interactions, including sharks that are discarded
dead, finned, or that experience post-release mortality, and therefore
there is some level of uncertainty in all available stock assessments
and abundance indices, particularly so in the South Atlantic and Indian
Oceans. However, stock assessments in the North Atlantic and North
Pacific were considered robust by the ERA Team. Some degree of
historical decline is indicated in all ocean basins, and population
declines are ongoing in the North Atlantic. In the South Pacific, there
are no available stock assessments, so the positive trends indicated
here are based on available studies with limited geographic scope.
Overall, there is no indication that global abundance has declined to
the point that reproductive success of the species has declined or
inbreeding has resulted, nor is there evidence of other depensatory
processes associated with small populations. All ERA Team members
agreed that the best available scientific and commercial information
indicates that the species' abundance does not put it at risk of
extinction currently. Several ERA Team members were of the opinion that
declining abundance trends would likely contribute to the species' risk
of extinction in the foreseeable future as they defined it; however,
the majority of ERA Team members concluded that global abundance trends
are unlikely to contribute significantly to the species' risk of
extinction currently or in the foreseeable future as they defined it.
We agree that this factor is not contributing significantly to the
species' risk of extinction now.
Over the foreseeable future of 50 years that we have determined is
more appropriate to apply for this species, we find that the best
available scientific and commercial data indicate that the abundance
factor is unlikely to significantly contribute to the species'
[[Page 68250]]
extinction risk. The shortfin mako shark population in the Pacific
Ocean basin (a major segment of the global population) is likely to be
stable and/or potentially increasing over this time period. Despite
historical levels of decline (estimated at 47-60 percent reduction in
total biomass) and likely continued decreases in the North Atlantic
until at least 2035 (there is the potential for the population to begin
rebuilding after this time with appropriate reduction of fishing
mortality through management measures), as well as potential continuing
population decreases of unknown degrees in the Indian and South
Atlantic Oceans, we conclude that the best available scientific and
commercial information indicates that global population abundance will
not likely decline to the point that will put the species at risk of
extinction over this timeframe.
Productivity
The shortfin mako shark exhibits high longevity (at least 28-32
years; Natanson et al. 2006; Dono et al. 2015), slow growth rates, late
age at maturity (6-9 for males and 15-21 years for females; Natanson et
al. 2006; Semba et al. 2009), long gestation (9-25 months; Mollet et
al. 2000; Duffy and Francis 2001; Joung and Hsu 2005; Semba et al.
2011), and long reproductive cycles (3 years; Mollet et al. 2000; Joung
and Hsu 2005). Cort[eacute]s (2016) determined that the intrinsic rate
of population increase (rmax) for Atlantic shortfin mako
sharks ranges from 0.036-0.134 yr-\1\. This was among the
lowest values calculated from 65 populations and species of sharks. The
ERA Team therefore concluded that the productivity of the species is
quite low. The species also exhibits low natural mortality (0.075-0.244
yr-\1\; Cort[eacute]s 2016) and a long generation time (25
years; Cort[eacute]s et al. 2015). Together, the species' life history
characteristics indicate that it is highly susceptible to depletion
from exploitation or other high-intensity sources of mortality, and
will recover slowly from declines brought on by such stressors. The ERA
Team was largely in agreement that although this factor doesn't
constitute a risk of extinction for the species currently, this factor
would likely contribute significantly to the species' risk of
extinction in the foreseeable future as they defined it, especially if
exacerbated by impacts of fishing mortality and resulting declines in
abundance. We agree that this factor is not contributing significantly
to the species' risk of extinction now. Similarly, we find that the
best available scientific and commercial data indicates that the
shortfin mako shark's low productivity will likely contribute
significantly to the species' extinction risk over the foreseeable
future of 50 years that we have determined is more appropriate to apply
for this species.
Spatial Structure/Connectivity
Shortfin mako sharks are globally distributed across all temperate
and tropical ocean waters and utilize numerous habitat types including
open ocean, continental shelf, shelf edge, and shelf slope habitats
(Rogers et al. 2015b; Corrigan et al. 2018; Francis et al. 2019; Rigby
et al. 2019; Santos et al. 2020; Gibson et al. 2021). This highly
migratory species is capable of undertaking movements of several
thousand kilometers (Kohler and Turner 2019; Francis et al. 2019), and
is able to make vertical migrations in the water column to several
hundred meters depth (Santos et al. 2021). As a red muscle endotherm,
the species is able to regulate its body temperature, allowing it to
tolerate a broad range of water temperatures (Watanabe et al. 2015).
Connectivity among ocean basins has been demonstrated by several
genetic studies. Taken together, results of available genetic analyses
suggest that female shortfin mako sharks exhibit fidelity to ocean
basins, while males readily move across the world's oceans and mate
with females from various basins, thereby homogenizing genetic
variability (Heist et al. 1996; Schrey and Heist 2003; Taguchi et al.
2011; Corrigan et al. 2018). The ERA Team unanimously agreed that,
based on this information, this demographic factor is not likely to
contribute significantly to the species' risk of extinction now or in
the foreseeable future as they defined it. We agree that this factor is
not contributing significantly to the species' risk of extinction now.
Over the foreseeable future of 50 years that we have determined is more
appropriate to apply for this species, we also find that this
demographic factor is not likely to significantly contribute to the
shortfin mako shark's risk of extinction because this factor is not
currently negatively affecting the species' status and the best
available scientific and commercial data suggests no basis to predict
that this factor will change over the extended time horizon.
Diversity
In its consideration of the degree to which diversity (or lack
thereof) might contribute to the extinction risk of the shortfin mako
shark, the ERA Team evaluated available information on genetic
diversity as well as diversity of distribution and ecology. Available
genetic studies do not indicate that the species has experienced a
significant loss of diversity that would contribute to extinction risk.
In fact, haplotype diversity has been found to be high in several
studies: 0.755 by Heist et al. (1996), 0.92 by Taguchi et al. (2011),
and 0.894 by Corrigan et al. (2018). Nucleotide diversity has been
found to be lower: 0.347 by Heist et al. (1996), 0.007 by Taguchi et
al. (2011), and 0.004 by Corrigan et al. (2018). Genetic studies
indicate a globally panmictic population, meaning that there is
sufficient movement of shortfin mako sharks, and therefore gene flow,
to reduce genetic differentiation among regions (Heist et al. 1996;
Schrey and Heist 2003; Taguchi et al. 2011; Corrigan et al. 2018). We
found no evidence that gene flow, migration, or dispersal has been
reduced. The species occurs across a variety of habitats and regions
(Rogers et al. 2015b; Rigby et al. 2019; Santos et al. 2020), and is
able to consume a diversity of prey (Stillwell and Kohler 1982;
Cort[eacute]s 1999; Maia et al. 2006; Gorni et al. 2012); these
characteristics protect against catastrophic events that may impact a
certain region or prey species. For these reasons, the ERA Team
unanimously agreed that it is not likely that this factor significantly
contributes to the species' risk of extinction now or in the
foreseeable future as they defined it. We agree that this factor is not
contributing significantly to the species' risk of extinction now.
Similarly, over the foreseeable future of 50 years that we have
determined is more appropriate to apply for this species, we also find
that this demographic factor is not likely to significantly contribute
to the shortfin mako shark's risk of extinction because this factor is
not currently negatively affecting the species' status and the best
available scientific and commercial data suggests there is no basis to
predict that this factor will change over the extended time horizon.
Summary and Analysis of Section 4(a)(1) Factors
As described above, section 4(a)(1) of the ESA and NMFS'
implementing regulations (50 CFR 424.11(c)) state that we must
determine whether a species is endangered or threatened because of any
one or a combination of the following factors: the present or
threatened destruction, modification, or curtailment of its habitat or
range; overutilization for commercial, recreational, scientific, or
educational purposes; disease or predation; the inadequacy of existing
regulatory mechanisms; or other natural or manmade factors affecting
its continued
[[Page 68251]]
existence. The ERA Team assembled the best available scientific and
commercial data and evaluated whether and the extent to which each of
the foregoing factors contributed to the overall extinction risk of the
global shortfin mako shark population. We summarize information
regarding each of these threats below according to the factors
specified in section 4(a)(1) of the ESA.
The Present or Threatened Destruction, Modification, or Curtailment of
Its Habitat or Range
The shortfin mako shark is a highly migratory, pelagic species that
spends time in a variety of open ocean and nearshore habitat types. The
species is globally distributed from about 50[deg] N (up to 60[deg] N
in the northeast Atlantic) to 50[deg] S. While distribution is
influenced by environmental variables including water temperature, prey
distribution, and DO concentration, the shortfin mako shark is able to
tolerate a broad thermal range and use a wide variety of prey
resources. The ERA Team agreed that because shortfin mako sharks have a
high adaptive capacity and do not rely on a single habitat or prey
type, they are able to modify their distributional range to remain in
an environment conducive to their physiological and ecological needs.
Additionally, there is no evidence that range contractions have
occurred, or that destruction or modification of their habitat on a
global scale has occurred to such a point that it has impacted the
status of the species. Therefore, the ERA Team concluded that the best
available scientific and commercial information indicates that loss
and/or degradation of habitat are not likely to be contributing
significantly to the extinction risk of the shortfin mako shark now or
in the foreseeable future as they defined it. We agree that this factor
is not contributing significantly to the species' risk of extinction
now. Because the contribution of habitat destruction, modification or
curtailment to extinction risk is not likely to change from 25 to 50
years, we also find that this factor will not contribute significantly
to extinction risk over the foreseeable future of 50 years that we have
determined is more appropriate to apply for this species.
An analysis of potential threats posed by pollutants and
environmental contaminants is carried out in Other Natural or Manmade
Factors Affecting its Continued Existence, below, because this
potential threat affects more than just the habitat or range of the
species.
Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
The best available information indicates that the primary threat
facing the shortfin mako shark is overutilization in fisheries. The
majority of the catch is taken incidentally in commercial fisheries
throughout the species' range, and the species is often
opportunistically retained due to the high value of its meat and fins
(Camhi et al. 2008; Dent and Clarke 2015). The species is targeted in
semi-industrial and artisanal fisheries in the Indian and Pacific
Oceans, and as a sportfish in several recreational fisheries, though
recreational fisheries are thought to have minimal contribution to the
species' overutilization in comparison to effects from commercial
fisheries.
Global reported catches of shortfin mako shark have risen
substantially since 1980. According to the Food and Agriculture
Organization of the United Nations (FAO) global capture production
statistics (accessible at https://www.fao.org/fishery/statistics-query/en/capture/capture_quantity), reported catch for shortfin mako shark in
the period 2010-2019 totaled 128,743 t, up from 86,912 t in the period
2000-2009 and 29,754 t in the period 1990-1999. In the 2010-2019 time
frame, reported landings in the Atlantic Ocean and adjacent seas
totaled 61,673 t (~48 percent of global reported catch), in the Pacific
Ocean totaled 43,927 t (~34 percent of global reported catch), and in
the Indian Ocean totaled 23,143 t (~ 18 percent of global reported
catch). Reported landings, however, represent a substantial
underestimate of actual catch because they do not fully account for
mortalities that result from fisheries interactions, including sharks
that are discarded dead, finned, or that experience post-release
mortality. For instance, Clarke et al. (2006) estimated that shark
biomass in the fin trade alone is three to four times higher than catch
reported in the FAO capture production data. Therefore, impacts of
commercial fishing fleets on the shortfin mako shark are likely much
greater than reported catch numbers suggest.
Data from across the species' range indicate that much of the catch
of shortfin mako sharks in longline fisheries is composed of immature
individuals (N Atlantic: Biton-Porsmoguer 2018, Coelho et al. 2020a; S
Atlantic: Barreto et al. 2016; NW Pacific: Ohshimo et al. 2016, Semba
et al. 2021; E Pacific: Furlong-Estrada et al. 2017, Salda[ntilde]a-
Ruiz et al. 2019, Doherty et al. 2014; Indian: Winter et al. 2020, Wu
et al. 2021). Exploitation of the juvenile life stage reduces the
proportion of the population that survives to maturity to reproduce.
Due to the late age-at-maturity of the species, many years are required
before conservation actions may influence the spawning population.
Additionally, abundance indices based on the part of the population
that is most vulnerable to fisheries mortality (immature individuals)
can be out of phase with those based on the abundance of the spawning
stock (e.g., CPUE and age-structured population models, respectively)
for decades. For these reasons, the delay between identifying
overutilization and addressing it can limit the effectiveness of
mitigation and can make fisheries management for the shortfin mako
shark difficult.
Rates of at-vessel mortality, or mortality resulting from
interactions with fishing gear prior to being brought onboard (also
known as hooking or capture mortality), vary by fishing practice and
gear type. Campana et al. (2016) estimated fisheries mortality of
shortfin mako sharks in Northwest Atlantic pelagic longline fisheries
targeting swordfish and tuna, in which the majority (88 percent) of
hooks used were circle hooks. The types of leaders or branch lines were
not reported. Shortfin mako sharks were found to experience a mean at-
vessel mortality rate of 26.2 percent, and another 23 percent of
incidentally caught shortfin mako sharks were injured at haulback
(Campana et al. 2016). The proportion of shortfin mako sharks that
experienced at-vessel mortality in pelagic longlines was significantly
higher than that of blue sharks (Prionace glauca), likely because
shortfin mako sharks have very high oxygen requirements, and their
ability to ram ventilate--or continuously force water across their
gills to breathe, typically by swimming at speed--is compromised once
hooked (Campana 2016; Campana et al. 2016). Data from Portuguese
longline vessels targeting swordfish in the North and South Atlantic
indicate at-vessel mortality rates of 35.6 percent for shortfin mako
shark (Coelho et al. 2012). This fleet uses stainless steel J hooks and
both monofilament and wire branch lines (Coelho et al. 2012). In the
North Pacific, shortfin mako sharks incidentally caught in the Hawaii
deep-set and American Samoa longline fisheries targeting tuna were
found to experience an at-vessel mortality rate of 22.7 percent
(Hutchinson et al. 2021). Prior to May 2022, the Hawaii deep-set
fishery used circle hooks, stainless steel braided wire leader, and
monofilament; the American Samoa longline fishery
[[Page 68252]]
uses circle hooks and all monofilament branch lines (Hutchinson et al.
2021). However, in May 2022, NMFS issued a final rule that prohibits
the use of wire leader in the Hawaii deep-set longline fishery, which
is anticipated to increase survivorship of incidentally caught sharks.
Post-release (or discard) mortality rates are more difficult to
accurately assess, although tag-recapture and telemetry studies
indicate that they can be relatively low for shortfin mako sharks
depending on factors such as hook type, hooking location, and handling.
Reported estimates of post-release mortality rate also depend on the
duration over which survival is assessed. Any mortality related to
capture and handling that occurs after the monitoring period would
cause post-release mortality rates to be underestimated (Musyl et al.
2009, Musyl and Gilman 2019). Campana et al. (2016) estimated that
shortfin mako sharks (n=26) caught incidentally in Northwest Atlantic
pelagic longlines have post-release mortality rates of 30-33 percent
over ~50 days. Bowlby et al. (2021) also investigated post-release
mortality in North Atlantic pelagic longline fleets, estimating a rate
of 35.8 percent for the species over the first 30 days from 104 tagging
events. The post-release mortality rate of tagged shortfin mako sharks
(n=35) after capture and release by pelagic longliners in the
Northeast, Northwest, Equatorial, and Southwest Atlantic was estimated
at 22.8 percent over the first 30 days (Miller et al. 2020). A
telemetry study on post-release mortality rates of five shark species
captured in the Hawaii deep-set and American Samoa tuna longline
fisheries found relatively low post-release mortality rates for
shortfin mako shark (6 percent), with only one mortality observed out
of 18 tags that reported (Hutchinson et al. 2021). A Bayesian analysis
of the post-release mortality rates from all sharks tagged (including
shortfin mako shark) found that post-release fate was correlated with
the animal's condition at the vessel, handling method, and the amount
of trailing gear left on the animals, whereby animals that were left in
the water and had most of the gear removed had the lowest mortality
rates (Hutchinson et al. 2021). Another telemetry study conducted by
the WCPFC in three longline fisheries in the South Pacific (New
Caledonia, Fiji and New Zealand) with much larger sample sizes (n = 57
shortfin mako shark tags) also found low post-release mortality rates
for shortfin mako sharks: 11.6 percent of the tagged, uninjured
shortfin mako sharks died within the 60-day monitoring period of the
tags, and this estimate increased to 63.2 percent for injured shortfin
mako sharks (Common Oceans (ABNJ) Tuna Project 2019). Similar to
conclusions from Hutchinson et al. 2021, survival rates were higher
when trailing gear was minimized, particularly in relation to the size
of the animal. Although the practice of hauling sharks on deck was not
found to have contributed to mortality, the probability of injury is
higher when sharks are hauled onboard, and injured sharks are less
likely to survive (Common Oceans (ABNJ) Tuna Project 2019). This
suggests that improvements to handling and release methods can help
reduce post-release mortality in shortfin mako shark and other shark
bycatch species.
In sum, bycatch mortality makes up a substantial amount of total
fishery mortality that is not captured in reported landings data. Total
non-landed fishery mortality for shortfin mako sharks in the Canadian
pelagic longline fishery was estimated at 49.3 percent (95 percent CI:
23-73 percent), indicating that even if retention of the species is
prohibited, about half of shortfin mako sharks hooked by this fleet
would die during or after fishing (Campana et al. 2016). Given that
other nations targeting swordfish and tuna in the Northwest Atlantic
and other ocean basins use similar gear configurations as used in the
study by Campana et al. (2016), similar un-reported mortality levels
may be expected if landings of shortfin mako shark were prohibited
throughout its global range. Hook type, gear configuration, handling
(i.e., bringing incidentally caught shortfin mako sharks on deck to
remove gear) (Bowlby et al. 2021), and bait type (Coelho et al. 2012;
Amorim et al. 2015; Fernandez-Carvalho et al. 2015) have been shown to
influence catch and mortality rates of shortfin mako sharks (see the
Status Review Report for a detailed review of this information).
In the North Atlantic Ocean, shortfin mako sharks are incidentally
caught mainly in pelagic and surface longlines, and to a lesser extent,
purse seines, bottom trawls, and gillnets. There are no commercial
fisheries targeting shortfin mako sharks in this region. Since 2017,
and until only recently, ICCAT Contracting Parties and Cooperating Non-
Contracting Parties (CPCs) have been required to release live North
Atlantic shortfin mako sharks in a manner that causes the least harm.
Retention of dead North Atlantic shortfin mako sharks remained
acceptable in many cases, and harvest of live individuals was only
permitted under very limited circumstances. Reported landings for all
CPCs in the North Atlantic (including dead discards) did decline in
recent years, though numbers remain high (3,281 t in 2015; 3,356 t in
2016; 3,199 t in 2017; 2,373 t in 2018; 1,882 t in 2019; 1,709 t in
2020) (SCRS 2021). Over 90 percent of recent shortfin mako shark catch
in the North Atlantic is attributable to Spain (longline fleet
targeting swordfish), Morocco (longline fleet targeting swordfish and
purse seine), and Portugal (longline fleet targeting swordfish), with
Spain harvesting nearly half of the North Atlantic catch in 2019 (866 t
reported). These three countries have each recently announced
unilateral retention bans. In early 2021, Spain announced a moratorium
on the landing, sale, and trade of North Atlantic shortfin mako shark.
The retention ban reportedly applies to 2021 catches from all Spanish
vessels, whether operating in domestic water or on the high seas, and
the ban on sale and trade extends to a 90 t stockpile of all mako shark
fins landed by Spanish vessels in 2020. Shortly afterwards, Portugal
announced a moratorium on landings of shortfin mako sharks caught in
the North Atlantic high seas fisheries, the source of the majority of
Portugal's mako shark catch. In February 2022, the government of
Morocco announced a 5-year national prohibition on the fishing,
storage, and trade of shortfin mako shark. Due to at-vessel and post-
release mortality, retention bans will not eliminate fishery mortality.
However, because approximately 50 percent of catches would be expected
to survive as discussed above, these retention bans may significantly
reduce shortfin mako shark mortality in pelagic longline fleets
operating in the North Atlantic, and therefore overall mortality in
this region.
Shortfin mako sharks are incidentally caught by the U.S. pelagic
longline fleets targeting swordfish and tuna (Thunnus spp.), including
in the Gulf of Mexico and the Caribbean Sea. A total of 2,406 t of
shortfin mako shark was landed and sold by this fishery between 1985
and 2008, valued at $4,562,402 (Levesque 2013). Commercial landings of
incidentally caught shortfin mako shark ranged from 17.6 t in 1985 to
266.8 t in 1993, with a mean of 100.24 t year\-1\ (Levesque 2013). As
described below in Inadequacy of Existing Regulatory Mechanisms, after
the 2017 ICCAT stock assessment indicated that North Atlantic shortfin
mako sharks were overfished and experiencing overfishing, the United
States took immediate action to end overfishing and work towards
[[Page 68253]]
rebuilding of the stock through emergency rulemaking. These measures
led to a reduction in North Atlantic shortfin mako shark landings by
the U.S. longline fleet, with 112 t landed in 2017, 42 t landed in
2018, and 33 t landed in 2019 (NMFS 2021). Shortfin mako shark catch in
U.S. pelagic longlines represented only 0.8 percent of total
international longline catch of the species across the entire Atlantic
Ocean in 2019 (NMFS 2021), and due to the poor reporting of other ICCAT
CPCs, this percentage is likely significantly lower. A detailed
overview of other fleets that contribute to shortfin mako shark
mortality in the North Atlantic can be found in the Status Review
Report.
Risk assessments have repeatedly found shortfin mako sharks to be
at high risk of overexploitation by pelagic longline fisheries in the
North Atlantic. Using an ecological risk assessment, the inflection
point of the population growth curve (a proxy for BMSY), and
IUCN Red List status, Simpfendorfer et al. (2008) found the shortfin
mako shark to have the highest risk among the pelagic shark species
taken in Atlantic longline fisheries. Similar results were found by
Cort[eacute]s et al. (2010) in an ecological risk assessment of 11
pelagic elasmobranchs across the North and South Atlantic, which
incorporated estimates of productivity (intrinsic rate of increase, r)
and susceptibility to the fishery (a product of the availability of the
species to the fleet, encounterability of the gear given the species'
vertical distribution, gear selectivity, and post-capture mortality).
The authors found the shortfin mako shark to be at high risk of
overexploitation (Cort[eacute]s et al. 2010). In an expanded
assessment, the shortfin mako shark's low productivity (r=0.058
year-\1\) and high susceptibility to capture (0.220,
calculated as the product of four factors: availability of the species
to the fleet, encounterability of the gear given the species' vertical
distribution, gear selectivity, and post-capture mortality) continued
to give the species one of the highest risks of overexploitation of
sharks caught by Atlantic pelagic longline fleets (Cort[eacute]s et al.
2015).
In the North Atlantic, fisheries mortality has led to substantial
population declines, and the stock is currently both overfished and
experiencing overfishing. ICCAT Recommendations 17-08 and 19-06 have
required live shortfin mako sharks to be released except in very
limited circumstances since 2017, though reported landings are still
high (1,709 t in 2020, inclusive of dead discards (SCRS 2021)). The ERA
Team considered whether a newly adopted retention prohibition
(Recommendation 21-09) would be adequate to reduce fishing mortality
and allow the stock to begin to rebuild, given that at-vessel mortality
will not be addressed by this measure. Given the status of the stock,
the continued high level of fishing effort, high catches, and low
productivity, the ERA Team concluded, and we agree, that the best
available scientific and commercial information indicates that
overutilization of shortfin mako shark is occurring in the North
Atlantic Ocean. Recent management measures may decrease the degree to
which overutilization threatens the species over the foreseeable future
(50 years), although this depends on whether current management
measures are effectively implemented, and whether additional management
measures, including measures addressing fishing gear and behavior, are
implemented in the future (this is discussed further in Inadequacy of
Existing Regulatory Mechanisms).
Shortfin mako sharks are frequently incidentally caught in pelagic
longlines in the South Atlantic, where fishing effort has been
increasing since the 1970s (Barreto et al. 2016). Recent reported
landings and dead discards of South Atlantic shortfin mako shark by all
ICCAT CPCs are as follows: 2,774 t in 2015; 2,765 t in 2016; 2,786 t in
2017; 3,158 t in 2018; 2,308 t in 2019; 2,855 t in 2020 (SCRS 2021). An
analysis of historical catches in longline fishing fleets in the South
Atlantic found three distinct phases of fishery exploitation: phase A
(1979-1997), characterized by the use of deep multifilament line with J
hooks to target tunas; phase B (1998-2007), during which monofilament
lines and circle hooks were used to target sharks and tunas, and phase
C (2008-2011), during which several measures regulating shark fishing
came into effect (Barreto et al. 2016). The authors found that
standardized catch rates of shortfin mako shark from a zero-truncated
model increased 8-fold in phase A (1979-1997), decreased by 55 percent
in phase B (1998-2007), and increased 1.3-fold in phase C (2008-2011),
even though nominal catch rates for all sharks combined were highest in
phase B. Dramatic catch rate declines in phase B coincided with
significant fishing effort increases as well as a lack of regulatory
measures, and Barreto et al. (2016) conclude that shortfin mako sharks
are depleted in the South Atlantic.
Significant contributors to South Atlantic shortfin mako shark
landings as reported by the ICCAT SCRS are Spain, Namibia, Brazil,
Portugal, and South Africa. Spanish longline fleets in the South
Atlantic reported shortfin mako shark catches of 1,049 t in 2017, 1,044
t in 2018, 1,090 t in 2019, and 799 t in 2020 (SCRS 2021). The Spanish
fleet has retained the vast majority of shortfin mako shark bycatch due
to the high value of the species. Therefore, catches and landings have
been roughly equivalent since the beginning of this fishery (Mejuto et
al. 2009). In Brazil, pelagic longline vessels targeting tuna have been
fishing since 1956, and part of the longline fleet shifted to targeting
swordfish in 1994 (Lucena Fr[eacute]dou et al. 2015). Although there
are no directed fisheries for shortfin mako shark in the South
Atlantic, the species is frequently retained due to its high value, and
is one of eight shark species commonly caught in the Brazilian longline
fleet (Lucena Fr[eacute]dou et al. 2015). Data from 2004-2010 indicate
that mako sharks (shortfin and longfin combined, though longfin are
rarely caught) were the second most common shark, making up 5.4 percent
of all individuals caught (Lucena Fr[eacute]dou et al. 2015). Reported
catch has been increasing in Brazil over the past few years: 124 t in
2016, 275 t in 2017, 399 t in 2018, 739 t in 2019, and 542 t in 2020
(no discards have been reported) (SCRS 2021). The South African pelagic
longline fleet targeting tuna and swordfish operates in South Africa's
Exclusive Economic Zone (EEZ) where the Southeast Atlantic meets the
Southwest Indian Ocean. Based on landings, logbook, and observer data,
the South African pelagic longline fleet was estimated to catch 50,000
shortfin mako sharks in 2015, with less than 1,000 estimated to have
been released in good condition (Jordaan et al. 2020). In total, 96
percent of hooked shortfin mako sharks were retained, and of those
discarded, 82 percent were dead (Jordaan et al. 2020). Most of the
shortfin mako shark catch occurred in waters of the Indian Ocean and
was, therefore, reported to the IOTC; smaller quantities of the species
are caught in Atlantic waters (Jordaan et al. 2020). There have been
steep increases in fishing effort (from 0.45 million hooks set in 2000
to 1.7 million hooks set in 2015) as well as shortfin mako shark
fishing mortality in the South African pelagic longline fleet (Jordaan
et al. 2018). Additional information on fishing practices of other
fleets that contribute to shortfin mako shark mortality in the South
Atlantic can be found in the Status Review Report.
In the South Atlantic, the shortfin mako shark has an overall 19
percent probability of being overfished with overfishing occurring
(ICCAT 2017). Data quality in the South Atlantic is
[[Page 68254]]
poor, and the stock assessment in this region has high uncertainty.
Therefore, given the high fishing effort and low productivity of the
species, the ERA Team concluded, and we agree, that the best available
scientific and commercial data indicate that overutilization may be
occurring in the South Atlantic.
In the Western and Central Pacific Ocean, shortfin mako sharks
commonly interact with longline fisheries and are more rarely targeted
by certain fleets. Fisheries information and catch data for this region
are available from the WCPFC, and although historical catch data are
lacking, reporting has improved in recent years with required reporting
of catches of key shark species. Despite reporting requirements, recent
catches of key shark species have not been provided to the WCPFC for a
number of longline fleets, including Indonesia, which is the top shark
fishing nation in the world (Dent and Clarke 2015; Okes and Sant 2019).
Fleets with the highest reported numbers of shortfin mako sharks caught
in recent years (as reported in WCPFC data catalogs available at
https://www.wcpfc.int/data-catalogue) include Taiwan, the United States
(Hawaii), Japan, Spain, and New Zealand. In the western North Pacific,
Taiwanese coastal and offshore longline fishing vessels mainly target
dolphinfish (also known as mahi mahi; Coryphaena hippurus), tunas, and
billfishes from April to October, and switch to targeting sharks by
changing gear configuration from November to March (Liu et al. 2021a).
Liu et al. (2021a) carried out a productivity-susceptibility analysis
for these Taiwanese fleets, where intrinsic rate of population growth
(r) was used to express productivity, and susceptibility was estimated
by multiplying catchability, selectivity, and post-capture mortality.
Based on the shortfin mako shark's low productivity (r = 0.0300) and
high susceptibility (1.1754), the authors found the species to be at
highest ecological risk. However, when conducting an integrated ERA
(incorporating the ERA, IUCN Red List index, annual body weight
variation trend, and the inflection point of population growth curve),
Liu et al. (2021a) found the species to be in the least risk group,
possibly because the average body weight of the species in the western
North Pacific has not experienced significant decline. The authors
found this result to be reasonable as the latest stock assessment for
North Pacific shortfin mako shark indicates that the stock is not
overfished and overfishing is not occurring. The shortfin mako shark is
one of the most commonly caught shark species in the Taiwanese large-
scale tuna longline fleet. Taiwan's catch of mako sharks (shortfin and
longfin) in all longline fleets as reported in WCPFC data catalogs are
high in the most recent 6 years of data: 1,216 t in 2015; 1,073 t in
2016; 1,088 t in 2017; 1,146 t in 2018; 1,680 t in 2019; and 1,665 t in
2020.
While there are no directed commercial fisheries for shortfin mako
sharks in Hawaii, the species is caught relatively frequently in the
Hawaii-based pelagic longline fishery targeting swordfish in the
shallow-set sector, and bigeye tuna (Thunnus obesus) in the deep-set
sector (Walsh et al. 2009; Carvalho 2021). Substantially higher numbers
of shortfin mako sharks are caught in the deep-set sector than the
shallow-set sector. From 1995-2006, shortfin mako sharks made up 2.9
percent of all observed shark catch in Hawaii-based pelagic longline
fisheries, with higher nominal CPUE rates in the shallow-set sector
than the deep-set sector (Walsh et al. 2009). Between 1995-2000 and
2004-2006, catch rates for shortfin mako sharks were stable for the
deep-set sector, and increased 389 percent in the shallow-set sector to
0.911 sharks per 1000 hooks (Walsh et al. 2009). Comparing the same two
time periods, minimum estimates of shortfin mako shark mortality
decreased in both the deep-set and shallow-set sectors (from 80.6 to 47
percent, and from 68 to 31.6 percent, respectively) (Walsh et al.
2009). This reduction in mortality may be a result of the prohibition
of shark finning in 2000, and the requirement of the use of relatively
large circle hooks rather than traditional J-hooks in the shallow-set
sector beginning in 2004 (Walsh et al. 2009; Carvalho et al. 2014).
Data from Hawaii and California-based Pelagic Longline Vessels Annual
Reports (available at https://www.fisheries.noaa.gov/resource/data/hawaii-and-california-longline-fishery-logbook-summary-reports)
indicate that from 2008 to 2019, Hawaii longline fisheries have
steadily increased the portion of mako catch that is released alive,
with 58 percent being released alive in 2008 and 89 percent being
released alive in 2019. Data from the report also shows that from 2008
to 2019, mako sharks comprised, on average, only 0.71 percent of all
species landed in the shallow-set and deep-set fisheries combined.
Additional information on other fleets that contribute to shortfin mako
shark mortality in the Western and Central Pacific Ocean can be found
in the Status Review Report.
Although historical catch data for the Western and Central Pacific
are lacking, reporting has improved in recent years with the
implementation of conservation and management measures that require
reporting of catches of key shark species. A noteworthy exception are
catches from Indonesia, recognized as the top shark fishing nation in
the world. Interactions with shortfin mako shark commonly occur in
pelagic longline fleets in this region. While RFMOs, and therefore
landings data, fishing practices, and regulatory measures, are divided
into the Eastern and Western and Central Pacific, abundance data in the
Pacific are separated by North and South Pacific. Therefore, we take
into consideration abundance data available for both the North and
South Pacific when assessing overutilization of the Western and Central
Pacific shortfin mako shark population. The latest stock assessment for
shortfin mako sharks in the North Pacific indicates that the stock is
not overfished and overfishing is not occurring, and CPUE trends from
the South Pacific indicate increasing shortfin mako shark abundance.
Based on the best available scientific and commercial data on current
and historical levels of fishing mortality and abundance, the ERA Team
concluded that overutilization is not likely occurring in the Western
and Central Pacific Ocean, and we agree.
In the Eastern Pacific Ocean, the species is mainly taken as
bycatch in commercial longline, drift gillnet, and purse seine fleets
(Read 2008). According to the Inter-American Tropical Tuna Commission's
(IATTC) Report on the tuna fishery, stocks, and ecosystem in the
Eastern Pacific Ocean in 2020, purse seine fisheries have contributed
very little to the take of mako sharks (Isurus spp.) in the Eastern
Pacific from 1993-2020 (estimated <3 t each year on average). Longline
vessels are a more important source of fishery mortality for the genus
in the Eastern Pacific Ocean. Estimated catch of mako sharks (Isurus
spp.) was 2,882 t in 2018 and 1,927 t in 2019, and the total estimated
catch in longlines from 1993-2019 was 36,036 t (IATTC 2020). The
California/Oregon drift gillnet fishery targeting swordfish and
thresher sharks incidentally catches shortfin mako sharks, the large
majority of which are retained. Annual landings of the species ranged
from 278 t in 1987 to 31 t in 2006, and have annually declined since
the late 1990s (Read 2008; Sippel et al. 2014). Analysis of NMFS
observer records from 1990-2015 indicates that shortfin mako sharks
make up only 4.92 percent of the total catch in this fishery (Mason et
al. 2019). Within Mexico's
[[Page 68255]]
EEZ in the Pacific, shortfin mako sharks are taken in the artisanal
fishery and the pelagic longline fishery, and were historically taken
in the drift gillnet fishery until 2010 (Sosa-Nishizaki et al. 2017).
Gillnet and longline fleets in Ecuador and Peru also contribute to
catch of the species in this region (Alfaro-Shigueto et al. 2010;
Doherty et al. 2014; Martinez-Ortiz et al. 2015). Additionally, despite
being defined as small-scale, Peruvian longline fisheries targeting
dolphinfish have a high magnitude of fishing effort and proportion of
juvenile shortfin mako sharks landed; this may have a large effect on
the population off of Peru. Additional information on other fleets that
contribute to shortfin mako shark mortality in the Eastern Pacific can
be found in the Status Review Report.
While RFMOs, and therefore landings data, fishing practices, and
regulatory measures, are divided into the Eastern and Western and
Central Pacific, abundance data in the Pacific are separated by North
and South Pacific. Therefore, we take into consideration abundance data
available for both the North and South Pacific when assessing
overutilization of the Eastern Pacific shortfin mako shark population.
The latest stock assessment for shortfin mako shark in the North
Pacific indicates that the stock is not overfished and overfishing is
not occurring. CPUE trends available from a variety of fisheries in the
South Pacific indicate population increases, although a stock
assessment is not available for this region. Despite this lack of a
cohesive population model, the available data indicate flat or
increasing abundance trends in the South Pacific. Based on the best
available scientific and commercial data on current and historical
levels of fishing mortality and abundance, the ERA Team concluded, and
we agree, that overutilization is not demonstrably occurring in the
Eastern Pacific Ocean, despite variation in the certainty associated
with estimates.
In the Indian Ocean, shortfin mako sharks are caught in pelagic
longline, gillnet, and purse seine fleets, with the majority of catch
coming from longlines targeting swordfish and sharks. Nominal reported
catches of sharks in the IOTC Convention area have generally been
increasing since the 1950s, though reporting of shark catches has been
very irregular and information on shark catch and bycatch is considered
highly incomplete (Murua et al. 2018). Fisheries catch data for the
Indian Ocean are available from the IOTC, which requires CPCs to
annually report shortfin mako shark catch data (IOTC Resolutions 17/05,
15/01, and 15/02). However, prior to the adoption of resolution 05/05
in 2005 (superseded by resolution 17/05 in 2017), there was no
requirement for sharks to be recorded at the species level in logbooks.
It was not until 2008 that some statistics became available on shark
catch, mostly representing retained catch and not accounting for
discards (IOTC 2018). Several countries continue to not report on their
interactions with bycatch species as evidenced by high rates of bycatch
reported by other fleets using similar gear configurations (IOTC 2018).
When catch statistics are provided, they may not represent total
catches of the species, but those simply retained on board, with
weights that likely refer to processed specimens (IOTC 2018).
Misidentification of shark species is also a common problem, and
reporting by species is very uncommon for gillnet fleets where the
majority of shark catches are reported as aggregates (IOTC 2020).
Reported shark catches dropped significantly after 2017 when India
stopped reporting aggregated shark catches and did not replace that
reporting with detailed reports by species. Decreases in reported shark
catches by Mozambique and Indonesia are thought to represent similar
reporting issues (IOTC 2020). In sum, although reporting has improved
substantially in recent years, there is a lack of historical data that
does not allow for establishment of long-term trends, and current
reported catches continue to be incomplete and largely underestimated.
The major contributors to mako shark (longfin and shortfin combined)
catch reported to IOTC are Japan, Madagascar, Indonesia, Spain, Sri
Lanka, Pakistan, Taiwan, South Africa, Portugal, and Guinea. A detailed
overview of fleets that contribute to shortfin mako shark mortality in
the Indian Ocean can be found in the Status Review Report.
Using the methodology of Cort[eacute]s et al. (2010), a preliminary
Productivity-Susceptibility Analysis for sharks caught in IOTC longline
fisheries revealed that shortfin mako sharks have among the highest
vulnerability to overexploitation in this fishery due to the species'
low productivity ([lambda]=1.061) and high susceptibility (0.929)
(Murua et al. 2012). In an updated ecological risk assessment of IOTC
longline, gillnet, and purse seine fisheries, Murua et al. (2018) found
that the most vulnerable species to the IOTC pelagic longline fleet is
the shortfin mako shark based on its low productivity ([lambda]=1.059)
and high susceptibility (0.867). Shortfin mako sharks had lower
susceptibility to catch in the purse seine and gillnet fisheries (0.129
and 0.318, respectively) and were therefore found to be less vulnerable
to overexploitation by these fleets (Murua et al. 2018). The post-
capture mortality rate in Indian Ocean purse seine fleets was reduced
between the 2012 and 2018 assessments due to the European fleet
implementing safe release best practices in 2014, but is still quite
high for shortfin mako sharks (approximately 55 percent) (Murua et al.
2018). Post-capture mortality represents the proportion of captured
animals that die as a result of interaction with the gear, calculated
as the sum of landings and dead discards (Cortes et al. 2010).
Available preliminary stock assessments for shortfin mako sharks in
the Indian Ocean indicate that overfishing is occurring but the stock
is not yet overfished. Underreporting of catch is suspected to be
continuing in this region, and the ERA Team therefore had low certainty
that these assessments accurately reflect the status of the species
here. However, recent CPUE trends in certain fleets indicate increasing
abundance trends in this region. The ERA Team concluded that, while
overutilization in commercial fisheries is likely impacting shortfin
mako sharks in the Indian Ocean, the severity of this threat is highly
uncertain. The best available scientific and commercial information on
current and historical levels of fishing mortality and abundance
indicates that overutilization is likely impacting the species in this
region to some degree, and will continue to impact the species in this
region over the foreseeable future (50 years).
Demand for shark products, specifically meat and fins, has rapidly
increased over the last 4 decades and has led to the overexploitation
of shark populations worldwide. While trade in shark fins appears to
have decreased slightly since the early 2000s, the trade in shark meat
has grown over the last decade or so (Dent and Clarke 2015). In fact,
domestic shark meat consumption in India is indicated to be the main
driver of local shark harvest rather than the global fin trade (Karnad
et al. 2020). The vast majority of shark fins in international trade
are imported into and consumed in East and Southeast Asia, including
China, Hong Kong, Taiwan, Singapore, Malaysia, and Vietnam, while the
largest importers and consumers of shark meat include Italy, Brazil,
Uruguay, and Spain (Dent and Clarke 2015). Spain, Indonesia, Taiwan,
and Japan are the major shark fin exporting producers, and as the trade
in shark meat has increased in recent years, these producers have also
begun exporting large volumes of shark meat to
[[Page 68256]]
the markets in Italy and Brazil (Dent and Clarke 2015). While available
data on the trade in shark products are incomplete due to inconsistent
identification of species and tracking of product types and volumes,
FAO statistics conservatively estimate the average declared value of
total world shark fin imports at $377.9 million per year from 2000-
2011, with an average annual volume imported of 16,815 t (Dent and
Clarke 2015). Annual average figures for shark meat from 2000-2011 were
107,145 t imported, worth $239.9 million (Dent and Clarke 2015).
Quantifying the amount of individual sharks harvested for the
international shark trade is more difficult given that a substantial
proportion of harvest is illegal, unregulated, or unreported (Clarke et
al. 2006b). Using shark fin trade data to estimate the total number of
sharks traded worldwide, Clarke et al. (2006b) found that between 26
and 73 million individual sharks of all species are traded annually
(median = 38 million each year), with a median biomass estimate of 1.70
million t per year (range: 1.21-2.29 million t each year).
Shortfin mako sharks are commonly retained for their highly valued
meat when incidentally caught, with fins often kept as a by-product
(Fowler et al. 2021). The meat is utilized fresh, frozen, smoked,
dried, and salted for human consumption (CITES 2019; Dent and Clarke
2015). Shortfin mako shark liver oil, teeth, jaws, and skin are also
traded, though most of these products are of lower value and are not
traded in significant quantities (CITES 2019).
The shortfin mako shark is a preferred species in the Hong Kong fin
market, one of the largest fin trading markets in the world (Fields et
al. 2018). Clarke et al. (2006a) analyzed 1999-2001 Hong Kong trade
auction data in conjunction with species-specific fin weights and
genetic information to estimate the annual number of globally traded
shark fins. The authors estimated that the shortfin mako shark makes up
approximately 2.7 percent (95 percent probability interval: 2.3-3.1
percent) of the Hong Kong shark fin trade, the fourth highest
proportion of auctioned fin weight after blue (17.3 percent),
hammerhead (Sphyrna zygaena or S. lewini, 4.4 percent) and silky
(Carcharhinus falciformis, 3.5 percent) sharks. This translates to an
estimated 300,000-1,000,000 shortfin mako sharks utilized in the global
shark fin trade each year, totaling between 20,000 and 55,000 t in
biomass (Clarke et al. 2006b). Although these data are fairly dated,
more recent studies demonstrate the continued prevalence of shortfin
mako shark fins in international trade. Fields et al. (2018) found
shortfin mako shark to be the ninth most commonly traded species in
Hong Kong based on random samples of fin trimmings from retail markets,
making up 2.77 percent of fin trimming samples and comprising 0.6
percent of modeled trimmings. In another recent study, shortfin mako
shark fins made up 4.16 percent and 2.37 percent of samples taken in
the fin markets of Guangzhou, the largest fin trade hub in mainland
China, and Hong Kong, respectively (Carde[ntilde]osa et al. 2020).
Shortfin mako sharks were listed under Appendix II of the
Convention on International Trade in Endangered Species of Wild Fauna
and Flora (CITES) effective November 26, 2019. As such, exports of the
species must be found to be non-detrimental to the survival of the
species in the wild and the specimen must have been legally acquired.
As the numbers presented above predate the CITES listing of shortfin
mako sharks, current levels of exploitation for the international trade
in meat and fins may be lower than prior to the listing (this
regulatory measure is discussed further in Inadequacy of Existing
Regulatory Mechanisms). With the trade in shark meat on the rise, the
preference for shortfin mako shark meat in addition to their continued
prevalence in the fin trade presents a concern for overutilization of
the species.
Several ERA Team members cited the estimation by Clarke et al.
(2006b) that 300,000-1,000,000 shortfin mako sharks may be utilized in
the global shark fin trade each year in their assessment of this
threat. Although this is not a recent study, and recent regulatory
mechanisms may reduce pressure from the fin trade on this species, this
estimate is still cause for concern given the low productivity of the
species. Considering the recent declines in the fin trade and increases
in the meat trade, the ERA Team generally concluded, and we agree, that
the preference for shortfin mako shark meat (in addition to fins)
presents a concern for overutilization of the species in the future.
After considering the best available scientific and commercial
data, several conclusions are indicated. Overall, although catch and
mortality data are underreported globally, with very low confidence in
data from both the Indian and South Atlantic Oceans, the ERA Team
recognized the ESA's requirement to consider the best scientific and
commercial data available, as summarized above and detailed in the
Status Review Report. The majority of ERA Team members concluded that
overutilization of the shortfin mako shark for commercial purposes (in
both fisheries and trade) is not likely currently significantly
contributing to the species' status but will likely contribute to the
extinction risk of the species in the foreseeable future as they
defined it, especially if management measures are inadequate. We agree
with the ERA Team that overutilization for commercial purposes is not
likely contributing significantly to the shortfin mako shark's risk of
extinction now. However, over the foreseeable future of 50 years that
we have determined is more appropriate to apply for this species, we
conclude that overutilization for commercial purposes is likely to
contribute to its risk of extinction. Recent management measures in the
North Atlantic (including retention prohibitions adopted by ICCAT and
by the top three shortfin mako shark-catching nations in the region)
indicate increasing international efforts to reduce the effects of
fishing mortality on the species in this region. Specifically,
Recommendation 21-09 prohibits harvest of live individuals (previously
allowed under limited circumstances) and contains strong provisions to
improve data reporting, and particularly, the catch reporting of live
releases and fish discarded dead. The measure does not require changes
to fishing behavior or gear, and therefore will not address at-vessel
or post-release mortality of incidentally caught shortfin mako sharks.
Because of ICCAT's track record of taking multilateral conservation and
management actions for the stock in response to indications of
declining status, we have a reasonable basis to predict that similar or
additional measures are likely to be continued or taken, as needed, to
ensure ICCAT's objectives of ending overfishing and rebuilding the
stock to levels that support MSY are met. While it is likely that the
level of overutilization in this region will decline to some degree
over the foreseeable future due to these efforts, it is unclear if
Recommendation 21-09 will reduce mortality to a point that will allow
the North Atlantic stock to rebuild. The low productivity of the
shortfin mako shark means that the biological response to the measure
will likely not be detectable for many years, despite assessment
efforts. Therefore, at this time it is not possible to assess the
adequacy of this measure to address the ongoing threat of overfishing
in the North Atlantic. In the South Atlantic Ocean, fishing effort has
been increasing
[[Page 68257]]
since the 1970s and there are no specific management measures at the
international level to address fishing mortality in this region. This
indicates that overutilization may increasingly impact the species over
the foreseeable future in this region. In the Indian Ocean,
overutilization will continue to impact the species over the
foreseeable future. Shortfin mako sharks in the Pacific Ocean are not
subject to overutilization at this time and there is no indication that
this will change significantly over the foreseeable future.
Recreational fishermen target shortfin mako sharks in certain
regions due to the high quality of their meat and the strong fight
experienced by the angler. In the U.S. Atlantic, recreational landings
of shortfin mako sharks have been significantly reduced after
management measures were implemented in 2018 and 2019. In the Pacific,
both U.S. and Australian recreational fisheries for the species are
largely catch-and-release. Further, population-level impacts of
recreational fishing at a global scale are unlikely to occur due to
vessel limitations that prevent the vast majority of the ``fleet'' from
accessing the whole of the species' habitat. For these reasons, the ERA
Team unanimously concluded that the best available scientific and
commercial data indicate that recreational fishing is unlikely to
contribute significantly to the species' risk of extinction now or in
the foreseeable future as they defined it. We agree that recreational
fishing is not contributing significantly to the species' risk of
extinction now. Over the foreseeable future of 50 years that we have
determined is more appropriate to apply for this species, we also find
that recreational fishing is not likely to significantly contribute to
the shortfin mako shark's risk of extinction because there is no basis
to predict that the impact of recreational fisheries on the species
will change over the extended time horizon.
Disease and Predation
Shortfin mako sharks are known to host a number of parasites, but
the ERA Team found no evidence that disease is impacting the status of
the species, nor any indication that disease may influence the species'
status in the foreseeable future.
The shortfin mako shark is a large apex predator with few natural
predators. Given current population estimates and distribution, impacts
from predation on a global scale are not likely to affect the species'
extinction risk. While climate change may cause changes to the marine
food web (and therefore, potentially influence predation on juvenile
shortfin mako sharks) over the next several decades, the ERA Team could
not accurately predict how these changes may impact the species.
The ERA Team concluded that the best available scientific and
commercial information indicates that neither disease nor predation are
factors that are contributing or will likely contribute significantly
to the species' extinction risk now or in the foreseeable future as
they defined it. We agree that neither disease nor predation are
contributing significantly to the species' extinction risk now. Over
the foreseeable future of 50 years that we have determined is more
appropriate to apply for this species, we also find that this factor is
not likely to significantly contribute to the shortfin mako shark's
risk of extinction because there is no basis to predict that this
factor will change over the extended time horizon.
Inadequacy of Existing Regulatory Mechanisms
The ERA Team evaluated existing regulatory mechanisms to determine
whether they may be inadequate to address threats to the shortfin mako
shark from overutilization. Below is a description and evaluation of
current and relevant domestic and international management measures
that affect the shortfin mako shark. More detailed information on these
management measures can be found in the Status Review Report.
U.S. Domestic Regulatory Mechanisms
The U.S. Secretary of Commerce has the authority to manage highly
migratory species (HMS) in the U.S. EEZ of the Atlantic Ocean, Gulf of
Mexico, and Caribbean Sea (16 U.S.C. 1811 and 16 U.S.C. 1854(f)(3)).
The Atlantic HMS Management Division within NMFS develops regulations
for Atlantic HMS fisheries and primarily coordinates the management of
HMS fisheries in federal waters (domestic) and the high seas
(international), while individual states establish regulations for HMS
in state waters. However, federally permitted shark fishermen are
required to follow federal regulations in all waters, including state
waters, unless the state has more restrictive regulations. For example,
the Atlantic States Marine Fisheries Commission (ASMFC) developed an
interstate coastal shark Fisheries Management Plan (FMP) that
coordinates management measures among all states along the Atlantic
coast (Florida to Maine) in order to ensure that the states are
following federal regulations. This interstate shark FMP became
effective in 2010.
Shortfin mako sharks in the Atlantic are managed under the pelagic
species complex of the Consolidated Atlantic HMS FMP. The first
Atlantic Shark FMP of 1993 classified the status of pelagic sharks as
unknown because no stock assessment had been conducted for this
complex. At that time, MSY for pelagic sharks was set at 1,560 t
dressed weight (dw), which was the 1986-1991 commercial landings
average for this group. However, as a result of indications that the
abundance of Atlantic sharks had declined, commercial quotas for
pelagic sharks were reduced in 1997. The quota for pelagic sharks was
then set at 580 t. In 1999, the U.S. FMP for Atlantic Tunas, Swordfish,
and Sharks implemented the following measures affecting pelagic sharks:
(1) reducing the recreational bag limit to one Atlantic shark per
vessel per trip, with a minimum size of 137 cm fork length for all
sharks; (2) increasing the annual commercial quota for pelagic sharks
to 853 t dw, apportioned between porbeagle (92 t), blue sharks (273 t
dw), and other pelagic sharks (488 t dw), with the pelagic shark quota
being reduced by any overharvest in the blue shark quota; and (3)
making bigeyed sixgill (Hexanchus nakamurai), bluntnose sixgill
(Hexanchus griseus), broadnose sevengill (Notorynchus cepedianus),
bigeye thresher, and longfin mako sharks, among other species,
prohibited species that cannot be retained.
The management measures for the conservation and management of the
domestic fisheries for Atlantic swordfish, tunas, sharks, and billfish
are published in the 2006 Consolidated HMS FMP and implementing
regulations at 50 CFR part 635 (71 FR 58058, October 2, 2006; NMFS
2006). Since 2006, this FMP has been amended 12 times, with four
additional amendments currently under development. Amendment 2,
finalized in June 2008, requires that all shark fins remain naturally
attached through landing in both the commercial and recreational
fisheries (73 FR 35778, June 24, 2008; corrected in 73 FR 40658, July
15, 2008). Limited exceptions to this requirement allowed by Amendment
9 (80 FR 73128, November 24, 2015) do not apply to shortfin mako
sharks.
Any fisherman who fishes for, retains, possesses, sells, or intends
to sell, Atlantic pelagic sharks, including shortfin mako sharks, needs
a Federal Atlantic Directed or Incidental shark limited access permit.
Generally, directed shark permits (which do not authorize the retention
of shortfin mako sharks at this time) allow fishermen to target sharks
while incidental permits
[[Page 68258]]
allow fishermen who normally fish for other species to land a limited
number of sharks. The permits are administered under a limited access
program and NMFS is no longer issuing new shark limited access permits.
To enter the directed or incidental shark fishery, fishermen must
obtain a permit via transfer from an existing permit holder who is
leaving the fishery. Until recently, under a directed shark permit,
there was no numeric retention limit for pelagic sharks, subject to
quota limitations (see below for a description of a recent final rule
regarding the retention limit for shortfin mako sharks). An incidental
permit allows fishermen to keep up to a total of 16 pelagic or small
coastal sharks (all species combined) per vessel per trip. Authorized
gear types include: pelagic or bottom longline, gillnet, rod and reel,
handline, or bandit gear. All fins must remain naturally attached. The
annual quota for pelagic sharks (other than blue sharks or porbeagle
sharks) is currently 488.0 t dw (Amendment 2 to the 2006 Consolidated
Atlantic HMS FMP (73 FR 35778, June 24, 2008; corrected version 73 FR
40658, July 15, 2008)).
NMFS monitors the catch of each of the different shark species and
complexes in relation to its respective annual quota and will close the
fishing season for each fishery if landings reach, or are projected to
reach, an 80 percent threshold of the available quota, and are also
projected to reach 100 percent of the available quota before the end to
the fishing year. Atlantic sharks and shark fins from federally
permitted vessels may be sold only to federally permitted dealers;
however, all sharks must have their fins naturally attached through
offloading. The head may be removed and the shark may be gutted and
bled, but the shark cannot be filleted or cut into pieces while onboard
the vessel. Logbook reporting is required for selected fishermen with a
federal commercial shark permit. In addition, fishermen may be selected
to carry an observer onboard, and some fishermen are subject to vessel
monitoring systems depending on the gear used and locations fished.
Since 2006, bottom longline and gillnet fishermen fishing for sharks
have been required to attend workshops to learn how to release sea
turtles and protected species in a manner that maximizes survival. In
2017, these workshops were modified to include a section on releasing
prohibited shark species. Additionally, NMFS published a final rule on
February 7, 2007 (72 FR 5633), that requires participants in the
Atlantic shark bottom longline fishery to possess, maintain, and
utilize handling and release equipment for the release of sea turtles,
other protected species, and prohibited shark species. In an effort to
reduce bycatch, NMFS has also implemented a number of time/area
closures with restricted access to fishermen with HMS permits who have
pelagic longline gear onboard their vessel.
The HMS Management Division also published an amendment to the 2006
Consolidated HMS FMP that specifically addresses Atlantic HMS fishery
management measures in the U.S. Caribbean territories (77 FR 59842,
October 1, 2012). Due to substantial differences between some segments
of the U.S. Caribbean HMS fisheries and the HMS fisheries that occur
off the mainland of the United States (including permit possession,
vessel size, availability of processing and cold storage facilities,
trip lengths, profit margins, and local consumption of catches), the
HMS Management Division implemented measures to better manage the
traditional small-scale commercial HMS fishing fleet in the U.S.
Caribbean Region. Among other things, this rule created an HMS
Commercial Caribbean Small Boat (CCSB) permit, which: allows fishing
for and sales of big-eye, albacore, yellowfin, and skipjack tunas,
Atlantic swordfish, and Atlantic sharks within local U.S. Caribbean
market; collects HMS landings data through existing territorial
government programs; authorizes specific gears; is restricted to
vessels less than or equal to 45 feet (13.7 m) length overall; and may
not be held in combination with any other Atlantic HMS vessel permits.
Until 2021, fishermen who held the CCSB permit were prohibited from
retaining any Atlantic sharks. However, at this time, fishermen who
hold the CCSB permit are prohibited from retaining shortfin mako
sharks, and are restricted to fishing for authorized sharks with only
rod and reel, handline, and bandit gear. Both the CCSB and Atlantic HMS
regulations have helped protect shortfin mako sharks while in the
Northwest Atlantic Ocean, Gulf of Mexico, and Caribbean Sea through
permitting, monitoring, quotas, and retention restrictions.
After the 2017 ICCAT stock assessment indicated that North Atlantic
shortfin mako sharks were overfished and experiencing overfishing, the
United States took action to end overfishing and take steps toward
rebuilding the stock through emergency rulemaking in March 2018. The
measures immediately required release of all live shortfin mako sharks
caught by commercial pelagic longliners with a minimum of harm while
giving due consideration to the safety of crew members, and only
allowed retention in pelagic longline gear if the shortfin mako shark
was dead at haulback. The measures required commercial fishermen using
non-pelagic longline gear (e.g., bottom longline, gillnet, handgear) to
release all shortfin mako sharks, alive or dead, with a minimum of harm
while giving due consideration to the safety of crew members. For
recreational fisheries, the emergency rulemaking increased the minimum
size limit for both male and female shortfin mako sharks to 83 inches
FL. These temporary measures were replaced by long-term management
measures finalized as Amendment 11 to the 2006 Consolidated HMS FMP in
March 2019. The final management measures for commercial fisheries
allowed retention of shortfin mako sharks caught with longline or
gillnet gears if sharks were dead at haulback. Further, vessels with
pelagic longline gear were required to have a functional electronic
monitoring system to verify condition for compliance purposes. For
recreational fisheries, the minimum size limit was increased from 54
inches to 71 inches FL for males and 83 inches FL for females, and the
use of circle hooks was required for all recreational shark fishing.
These measures led to the reduction of the United States' total
landings of North Atlantic shortfin mako shark (commercial and
recreational) from 302 t in 2017, to 165 t in 2018, to 57 t in 2019,
with 2 t of dead discards, an 81 percent reduction from 2017. In 2020,
U.S. recreational landings of North Atlantic shortfin mako shark were
24 t, reduced by over 90 percent from the 2013-2017 average.
Following the adoption of Recommendation 21-09 at the November 2021
ICCAT annual meeting (described further below), NMFS published a final
rule to implement a flexible shortfin mako shark retention limit with a
default limit of zero in all commercial and recreational HMS fisheries
(87 FR 39373; July 1, 2022). The rule meets domestic management
objectives, implements Recommendation 21-09, and acknowledges the
possibility of future retention (limited retention of shortfin mako
sharks may be allowed in 2023 and future years if ICCAT determines that
fishing mortality is at a low enough level North Atlantic-wide to allow
retention consistent with the conservation objectives of the
recommendation). The rule, effective July 5, 2022, requires that all
commercial and recreational fishermen
[[Page 68259]]
release all shortfin mako sharks, whether dead or alive, at haulback.
Any sharks released alive must be released promptly in a manner that
causes the least harm to the shark.
In the U.S. Pacific, HMS fishery management is the responsibility
of adjacent states and three regional management councils that were
established by the Magnuson-Stevens Fishery Conservation and Management
Act (MSA): the Pacific Fishery Management Council (PFMC), the North
Pacific Fishery Management Council (NPFMC), and the Western Pacific
Regional Fishery Management Council (WPRFMC). Based on the range of the
shortfin mako shark, only the PFMC and WPRFMC directly manage the
species.
The PFMC's area of jurisdiction is the EEZ off the coasts of
California, Oregon, and Washington. Prior to the development of a West
Coast-based FMP for HMS, the fisheries were managed by the states of
California, Oregon, and Washington, although some federal laws also
applied. In late October 2002, the PFMC adopted its FMP for U.S. West
Coast HMS Fisheries. This FMP's management area also covers adjacent
high seas waters for fishing activity under the jurisdiction of the HMS
FMP. The final rule implementing the HMS FMP was published in the
Federal Register on April 7, 2004 (69 FR 18443). Since its
implementation, this FMP has been amended five times, most recently in
2018. The FMP requires a federal permit for all commercial HMS vessels
that fish for HMS off of California, Oregon or Washington, or land HMS
in these states. The permit is endorsed with a specific endorsement for
each gear type to be used, and any commercial fisher may obtain the
required gear endorsements. Legal HMS gear includes harpoon, surface
hook and line, large mesh drift gillnet, purse seine, and pelagic
longline; however, the use of these gears are subject to state
regulatory measures. For commercial passenger recreational fishing
vessels, a federal permit is required by the FMP, though existing state
permits or licenses for recreational vessels can meet this requirement.
Legal recreational gear includes rod-and-reel, spear, and hook and
line. Per the FMP, due to the stock's vulnerability, possible
importance of the U.S. West Coast EEZ as nursery habitat, and poorly
known total catches and extent of the stock, the recommended harvest
guideline for shortfin mako sharks is 150 t round weight. This harvest
guideline is a general objective, not a quota. Although attainment of a
harvest guideline doesn't require management action such as closure of
the fishery, it does prompt a review of the fishery.
The WPRFMC's area of jurisdiction is the EEZs of Hawaii,
Territories of American Samoa and Guam, Commonwealth of the Northern
Mariana Islands, and the Pacific Remote Island Areas, as well as the
domestic fisheries that occur on the adjacent high seas. The WPRFMC
developed the Fishery Ecosystem Plan for Pacific Pelagic Fisheries of
the Western Pacific Region (FEP; formerly the Fishery Management Plan
for the Pelagic Fisheries of the Western Pacific Region) in 1986 and
NMFS, on behalf of the U.S. Secretary of Commerce, approved the Plan in
1987. Since that time, the WPRFMC has recommended, and NMFS has
approved, numerous amendments to the Plan as necessary for conservation
and management purposes. The WPRFMC manages HMS fisheries pursuant to
the FEP, and species that are managed under FMPs or FEPs are called
Management Unit Species (MUS), and typically include those species that
are caught in quantities sufficient to warrant management or specific
monitoring by NMFS and the Council. In the FEP, shortfin mako sharks
are designated as a Pelagic MUS and, thus, are subject to regulations
under the FEP. These regulations are intended to minimize impacts to
targeted stocks as well as protected species. Fishery data are also
analyzed in annual reports and used to amend the FEP as necessary.
In addition to fishing regulations for highly migratory species,
the United States has implemented several significant laws for the
conservation and management of sharks. The Tuna Conventions Act of
1950, Atlantic Tunas Convention Act of 1975, and Western and Central
Pacific Fisheries Convention Implementation Act (enacted in 2007)
authorize the U.S. Secretary of Commerce to promulgate regulations for
U.S. vessels that fish for tuna or tuna-like species in the IATTC,
ICCAT, and WCPFC Convention areas, respectively. The MSA, originally
enacted in 1976, is the primary law governing marine fisheries
management in U.S. federal waters (3-200 miles offshore), and aims to
prevent overfishing, rebuild overfished stocks, increase long-term
economic and social benefits, and ensure a safe and sustainable supply
of seafood. The MSA created eight regional fishery management councils,
whose main responsibility is the development and subsequent amendment
of FMPs for managed stocks. The MSA requires NMFS to allocate both
overfishing restrictions and recovery benefits fairly and equitably
among sectors of the fishery. In the case of an overfished stock, NMFS
must establish a rebuilding plan through an FMP or amendment to such a
plan. The FMP or amendment to such a plan must specify a time period
for ending overfishing and rebuilding the fishery that shall be as
short as possible, taking into account the status and biology of the
stock, the needs of fishing communities, recommendations by
international organizations in which the United States participates,
and the interaction of the overfished stock within the marine
ecosystem. The rebuilding plan cannot exceed ten years, except in cases
where the biology of the stock, other environmental conditions, or
management measures under an international agreement in which the
United States participates dictate otherwise.
The Shark Finning Prohibition Act of 2000 prohibits any person
under U.S. jurisdiction from: (i) engaging in the finning of sharks;
(ii) possessing shark fins aboard a fishing vessel without the
corresponding carcass; and (iii) landing shark fins without the
corresponding carcass, among other things. The Shark Conservation Act
of 2010 strengthened shark finning measures by prohibiting any person
from removing shark fins at sea (with a limited exception for smooth
dogfish, Mustelus canis); or possessing, transferring, or landing shark
fins unless they are naturally attached to the corresponding carcass.
Management measures implemented in response to the status of the
North Atlantic shortfin mako shark stock were finalized in March 2019,
and have been effective in reducing U.S. landings of the species in
this region (both recreationally and commercially) as previously
discussed. NMFS recently published a final rule to implement ICCAT
Recommendation 21-09, requiring that all U.S. commercial and
recreational fishermen release all shortfin mako sharks, whether dead
or alive, at haulback. The adequacy of this retention prohibition
cannot be assessed at this time; as data for each fishing year is not
reported until the following calendar year, the effect of this measure
will not be easily assessed until 2024 when the landings and discard
data from 2023 can be analyzed. In the Pacific, the available stock
assessment for the North Pacific region indicates that the species is
neither overfished nor experiencing overfishing (ISC Shark Working
Group 2018). For the foregoing reasons, it is likely that U.S. domestic
fisheries management measures are adequate to address threats of
overfishing to the species in U.S. waters. With regard to the fin and
meat trade, declines in U.S. exports of shark fins
[[Page 68260]]
followed implementation of both the Shark Finning Prohibition Act and
the Shark Conservation Act, and recent declines in the mean value of
U.S. exports per metric ton have been reported by NMFS. Additionally,
14 U.S. states and three U.S. territories have enacted legislation
controlling shark finning by banning possession and sale of shark fins
(see details in the Status Review Report). These state laws have
reduced U.S. landings of sharks and therefore U.S. trade and
consumption of shark fins, although it is important to note that the
United States has traditionally played a relatively minimal role in the
global shark fin trade (0.3 and 0.4 percent of global imports and
exports in U.S. dollars according to Ferretti et al. 2020). Measures
that prohibit the possession and sale of shark fins may provide some
limited conservation benefit to sharks, including the shortfin mako
shark, by discouraging the landing of any sharks. The ERA Team
therefore concluded that the best available scientific and commercial
data indicate that U.S. domestic regulatory measures are adequate to
manage impacts from fisheries on the species in U.S. waters, as
evidenced by the reduction in U.S. shortfin mako shark catch
(commercial and recreational) in the Atlantic following the 2017 ICCAT
stock assessment, stable population status in the North Pacific, and
strong prohibitions on shark finning for those subject to U.S.
jurisdiction. We agree with their assessment.
International Regulatory Mechanisms
Despite adequate management in U.S. waters, the ERA Team concluded
that regulatory measures to address threats of incidental catch,
targeted catch (in certain limited areas and fleets), and trade across
the species' range may not be adequate in certain regions.
RFMOs that manage HMS play perhaps the most significant role in
regulating catch and mortality of shortfin mako sharks in commercial
fisheries worldwide. Of the four major RFMOs that manage shortfin mako
sharks, only ICCAT has management measures specific to the species,
while IATTC, WCPFC, and IOTC have general shark management measures.
ICCAT is the main international regulatory body for managing
shortfin mako sharks on the high seas in the Atlantic Ocean. In 2004,
following the development and implementation of the International Plans
of Action for Conservation and Management of Sharks (IPOA-Sharks),
ICCAT adopted Recommendation 04-10 requiring CPCs to annually report
data for catches of sharks, including available historical data. This
Recommendation specifically called for the SCRS to review the
assessment of shortfin mako sharks and recommend management
alternatives for consideration by the Commission, and to reassess the
species no later than 2007. In 2005, ICCAT adopted Recommendation 05-
05, which amended Recommendation 04-10 by requiring CPCs to annually
report on their implementation of the Recommendation, and instructing
those that have not yet implemented this recommendation to reduce North
Atlantic shortfin mako shark mortality to implement it and report to
the Commission. In 2006, ICCAT adopted Recommendation 06-10, which
further amended Recommendation 04-10 and called for a shortfin mako
shark stock assessment in 2008. A supplemental Recommendation by ICCAT
(07-06, adopted in 2007 and entered into force in 2008) called for CPCs
to submit catch data including estimates of dead discards and size
frequencies in advance of SCRS assessments, to take appropriate
measures to reduce fishing mortality for the North Atlantic shortfin
mako shark, and to implement research on pelagic sharks in the
Convention area to identify potential nursery areas. Recommendation 10-
06 (adopted in 2010 and entered into force in 2011) instructed CPCs to
report on how they have implemented the three recommendations described
above, particularly steps they have taken to improve data collection
for direct and incidental catches. It also recommended that CPCs that
do not report catch data for shortfin mako sharks be prohibited from
retaining the species, and that the SCRS conduct a stock assessment for
shortfin mako sharks in 2012. Recommendation 14-06 (adopted in 2014 and
entered into force in 2015) replaced and repealed Recommendations 05-05
and 10-06, among others, and it calls for CPCs to improve data
collection for shortfin mako shark and report information on domestic
catch of shortfin mako shark to ICCAT and encourages CPCs to undertake
research on biology and life history of the shortfin mako shark.
Based on the 2017 shortfin mako shark stock assessment, which
concluded there was a 90 percent probability of the stock being in an
overfished state and experiencing overfishing (as discussed previously
in Abundance and Trends), the Commission adopted Recommendation 17-08
(adopted in 2017 and entered into force in 2018), requiring CPCs to
release North Atlantic shortfin mako sharks in a manner that causes the
least harm. Retention of dead North Atlantic shortfin mako sharks
remained acceptable in many cases, and harvest of live shortfin was
only permitted under very limited circumstances. In 2019, the SCRS
carried out new projections for North Atlantic shortfin mako shark
through 2070 (two generation lengths) at the Commission's request
(projections are described above in Abundance and Trends). Multiple TAC
options with associated time frames and probabilities of rebuilding
were presented to the Commission. Based on the resulting negative
projections and high susceptibility of the species to overexploitation,
and to accelerate the rate of recovery and to increase the probability
of success, the SCRS recommended that the Commission adopt a non-
retention policy without exception. While a non-retention policy would
ostensibly reduce mortality, shortfin mako sharks frequently interact
with surface longline fisheries and the potential inability for
fishermen to avoid the species may not lead to sufficient decreases in
mortality. Therefore, the SCRS noted that other management measures,
such as time-area closures, reduction of soak time, safe handling, and
best release practices may also be required (ICCAT 2019).
In 2019, several countries presented proposals to end overfishing
and rebuild the North Atlantic stock of shortfin mako shark; however,
none were ultimately adopted (see Status Review Report for more
detail). The United States, Senegal, Canada, the EU, and Morocco met
several times to discuss the proposals, but were unable to reach
agreement on the elements of a combined measure. In a proposal
presented by the ICCAT Chair and adopted in 2019 (Recommendation 19-
06), it was agreed to extend and update the existing provisions in
Recommendation 17-08. Recommendation 19-06 also urged the Commission to
adopt a new management recommendation for the North Atlantic shortfin
mako shark at its 2020 annual meeting in order to establish a
rebuilding plan with a high probability of avoiding overfishing and
rebuilding the stock to BMSY within a timeframe that takes
into account the biology of the stock. Due to the COVID-19 pandemic,
however, ICCAT did not host an annual meeting in 2020 and management
decisions were made through a correspondence process. Due to the
difficulty associated with this process, no consensus could be made on
a new measure and Recommendation 19-06 remained in place.
[[Page 68261]]
In 2021, the ICCAT annual meeting was conducted virtually and the
conservation of the North Atlantic shortfin mako shark stock was a
priority. Commission members reached consensus on Recommendation 21-09,
which puts into place a 2-year retention ban that aims to reduce
mortality and establishes a process to evaluate if and when retention
may be allowed in the future, in line with scientific advice. The
measure contains strong provisions to improve data reporting, and
particularly, the catch reporting of live releases and fish discarded
dead, by all ICCAT parties. This measure entered into force on June 17,
2022, and as data for each fishing year is not reported until the
following calendar year, the management effect of Recommendation 21-09
will not be easily assessed until 2024 when the landings and discard
data from 2023 can be analyzed. Despite this important step forward,
ICCAT's work to end overfishing and rebuild North Atlantic shortfin
mako shark is not complete; within Recommendation 21-09 a provision
exists to revisit the measure ``no later than 2024 to consider
additional measures to reduce total fishing mortality.'' Future efforts
will likely be focused on reducing the at-haulback and post-release
mortality of North Atlantic shortfin mako shark unintentionally
captured alongside target species.
The low productivity of the shortfin mako shark means that the
biological response to the recently adopted ICCAT measure will likely
not be detectable for many years, despite assessment efforts.
Therefore, at this time it is not possible to assess the adequacy of
this measure to address the ongoing threat of overfishing in the North
Atlantic. The ERA Team raised some concerns and uncertainties with
regard to Recommendation 21-09. The measure does not require changes to
fishing behavior or gear, and therefore will not address at-vessel or
post-release mortality of incidentally caught shortfin mako sharks.
Based on recent reported landings allowed under Recommendation 19-06
indicating high numbers of shortfin mako sharks dead at-haulback, it is
unclear if Recommendation 21-09 will reduce mortality to a point that
will allow the North Atlantic stock to rebuild. It is also unclear what
measures will be in place after the 2-year period ends.
The IATTC is responsible for the conservation and management of
tuna and other pelagic species in the Eastern Pacific. There are
currently no specific resolutions related to the management of shortfin
mako shark; however, IATTC does have resolutions relating to sharks in
general. Resolution C-16-05 on the management of shark species requires
that purse-seine vessels promptly release any shark that is not
retained as soon as it is seen in the net or on deck, and includes
provisions for safe release of such sharks. Resolution C-05-03 requires
that fins onboard vessels total no more than 5 percent of the weight of
sharks onboard. The IATTC requires 100 percent observer coverage
onboard the largest purse seine vessels, and 5 percent observer
coverage on larger longline vessels.
The WCPFC is responsible for the conservation and management of
highly migratory species in the Western and Central Pacific Ocean. The
WCPFC aims to address issues related to the management of high seas
fisheries resulting from unregulated fishing, over-capitalization,
excessive fleet capacity, vessel re-flagging to escape controls,
insufficiently selective gear, unreliable databases, and insufficient
multilateral cooperation with respect to conservation and management of
highly migratory fish stocks. There are currently no management
measures specific to shortfin mako sharks in the WCPFC; however, their
management is addressed under the Conservation and Management Measure
for Sharks (CMM 2019-04). This measure prohibits finning, requires that
vessels land sharks with their fins naturally attached, and calls for
vessels to reduce bycatch and practice safe release of sharks. In order
to reduce bycatch mortality, the measure calls for longline fisheries
targeting billfish and tuna to either not use wire branch lines or
leaders, or not use shark lines (branch lines running directly off
longline floats or drop lines). Further, the measure requires catches
of key shark species to be reported to the Commission annually.
In Indian Ocean waters, the IOTC serves to promote cooperation
among CPCs to ensure, through appropriate management, the conservation
and optimum utilization of stocks, and encourage sustainable
development of fisheries based on such stocks. The United States is not
a member. Conservation and management measures are adopted in the form
of either resolutions, which require a two-thirds majority of Members
present and voting to adopt them and are binding for contracting
parties, or recommendations, which are non-binding and rely on
voluntary implementation. While a number of measures have been adopted
by IOTC parties that apply to sharks and bycatch in general, there are
currently no specific resolutions related to the management of shortfin
mako shark (see IOTC 2019). In Resolution 15/01 on the recording of
catch and effort by fishing vessels in the IOTC area of competence, all
purse seine, longline, gillnet, pole and line, handline, and trolling
fishing vessels are required to have a data recording system and
provide aggregated data to the Secretariat each year. Resolution 15/02
mandates statistical reporting requirements for IOTC CPCs by species
and gear for all species under the IOTC mandate as well as the most
commonly caught elasmobranch species and lays out requirements for
observer coverage. IOTC Resolution 17/05 on the conservation of sharks
caught in association with fisheries managed by IOTC requires that
sharks landed fresh not have their fins removed prior to first landing,
and for sharks landed frozen, CPCs must abide by the 5 percent fins-to-
carcass weight ratio. Further, CPCs must report data for catches of
sharks including all available historical data, estimates and life
status of discards (dead or alive), and size frequencies under this
resolution. Despite these requirements, reporting of shark catches has
been very irregular and information on shark catch and bycatch is
considered highly incomplete (Murua et al. 2018). A number of countries
continue to not report on their interactions with bycatch species as
evidenced by high rates of bycatch reported by other fleets using
similar gear configurations (IOTC 2018). The lack of reliable records
of catch and lack of a formal stock assessment make it difficult to
determine whether the regulatory mechanisms described above are
adequate to address overutilization of the species in the Indian Ocean.
Regarding the general shark conservation measures in place for
WCPFC, IATTC, and IOTC, the ERA Team had concerns regarding low
compliance with reporting requirements, especially in the Indian Ocean
and South Atlantic Ocean. The lack of reliable catch data in these
regions, as well as a lack of formal stock assessments in the Indian
Ocean and South Pacific Ocean, make it difficult to assess whether
regulatory mechanisms in these areas are adequate to address threats of
overutilization to the species.
As the shortfin mako shark is highly valued for both its meat and
fins, regulatory mechanisms ensuring that trade does not lead to
overexploitation are critical to the species' survival. Many individual
countries and RFMOs have implemented measures to curb the practice of
shark finning and the sale of or trade in shark products over the last
decade (see detailed information in the Status Review Report), and the
shortfin
[[Page 68262]]
mako shark was listed on Appendix II of CITES as of November 2019.
CITES is an international convention that aims to ensure that
international trade in animals and plants does not threaten their
survival, and while CITES regulates international trade, it does not
regulate take or trade within a country. Appendix II includes species
not necessarily threatened with extinction, but trade must be
controlled to ensure utilization is compatible with their survival. As
an Appendix II-listed species, international trade in specimens of
shortfin mako shark is allowed with an export permit, re-export
certificate, or introduction from the sea certificate granted by the
proper management authority. The above permits or certificates may be
granted if the trade is found to be non-detrimental to the survival of
the species in the wild and the specimen was found to have been legally
acquired. A number of countries have taken a reservation to the listing
(Botswana, Democratic Republic of the Congo, Eswatini, Japan, Namibia,
Norway, South Africa, United Republic of Tanzania, Zambia, and
Zimbabwe) meaning they have made a unilateral decision to not be bound
by the provisions of CITES relating to trade in this species.
Although the CITES listing is a positive step to ensure the
sustainability of the international trade of shortfin mako sharks, it
is difficult to assess the effectiveness of this measure over such a
short period of time. An analysis of trade data and fin trimmings from
a Hong Kong market led Carde[ntilde]osa et al. (2018) to conclude that
compliance with reporting and permitting requirements for CITES-listed
shark species listed at the 16th CITES Conference of the Parties (2013)
was low in 2015-2016. Therefore, the CITES listing of shortfin mako
shark may not have a strong impact on the number of individuals
harvested for the international fin and meat trades. While the fin
trade has declined, recent increases in the trade of shark meat signify
the continued need for regulatory mechanisms to address the threat of
overutilization in the international fin and meat trades.
Overall, while the ERA Team recognized the strong regulatory
measures in place for shortfin mako sharks in U.S. domestic waters,
retention bans that have been put in place for the species in several
countries and recently by ICCAT, and increased global efforts to end
shark finning, the ERA Team expressed concern about the adequacy of
existing regulatory mechanisms to monitor and manage mortality from
fisheries interactions on the high seas and the international meat and
fin trade. The ERA Team was split on how this factor contributes to the
extinction risk of the species, with just over half of the group
concluding that the inadequacy of existing regulatory mechanisms will
likely contribute significantly to the species' risk of extinction in
the foreseeable future as they defined it, but is not likely
contributing to the species' extinction risk currently. The remaining
members found it unlikely that this factor is significantly
contributing to the species' extinction risk now or would do so in the
foreseeable future as they defined it. We agree with the ERA Team's
assessment that the inadequacy of existing regulatory mechanisms is not
likely contributing to the species' risk of extinction currently. Over
the foreseeable future of 50 years that we have determined is more
appropriate to apply for this species, we find that existing regulatory
mechanisms may be inadequate to address overutilization, especially
given the species' low productivity and prevalence in both meat and fin
markets.
Other Natural or Manmade Factors Affecting Its Continued Existence
Under this factor, the ERA Team considered potential threats posed
by pollutants and environmental contaminants, climate change, and shark
control/bather protection efforts.
As high-level predators, shortfin mako sharks bioaccumulate and
biomagnify heavy metals and organic contaminants; however, the impacts
of these pollutants on the physiology and productivity of the species
(and sharks in general) are poorly studied. While results of few
available studies of other species of sharks and fish provide some
evidence that sharks may experience negative physiological impacts and
potentially reduced fitness as a result of contaminant exposure, the
ERA Team found no evidence that individuals or populations are
adversely affected to a degree that would impact the status of the
species. Therefore, the ERA Team unanimously agreed that pollutants and
environmental contaminants are unlikely to be contributing
significantly to the species' extinction risk now or in the foreseeable
future as they defined it. We agree that pollutants and environmental
contaminants are not likely contributing significantly to the species'
extinction risk now. Over the foreseeable future of 50 years that we
have determined is more appropriate to apply for this species, we find
that pollutants and environmental contaminants are not likely to
significantly contribute to the shortfin mako shark's risk of
extinction because this factor is not currently negatively affecting
the species' status and the best available scientific and commercial
data suggests no basis to predict that this will change over the
extended time horizon.
When considering the potential threat of climate change to the
shortfin mako shark, the ERA Team considered projected impacts to the
marine environment (including warming waters, acidification, and
shifting habitat suitability and prey distributions), and the species'
potential responses to these impacts. While long-term climate
projections (through 2100) are available and considered reliable, the
ERA Team found that the species' responses to these projected
environmental changes that far into the future could not be predicted
with any certainty. While some studies predict that the species may be
subject to significant habitat loss and potential behavioral and
fitness impairments by 2100, the shortfin mako shark's broad prey base
and thermal tolerance, among other factors, may give them a high
adaptive capacity. A detailed review of available studies can be found
in the Status Review Report. The majority of the ERA Team considered it
unlikely that climate change is currently contributing to the species'
extinction risk, or will contribute to the species' extinction risk in
the foreseeable future as they defined it. Several ERA Team members
concluded that the contribution of climate change to the extinction
risk of the species in the foreseeable future could not be determined
due to the lack of available information on the species' response to
climate change. We agree that the best available scientific and
commercial information indicates that climate change is not
significantly contributing to the species' extinction risk now. Over
the foreseeable future of 50 years that we have determined to be more
appropriate to apply for this species, we also find that climate change
is not likely to significantly contribute to the shortfin mako shark's
risk of extinction because it is not currently negatively affecting the
species' status and the best available scientific and commercial data
suggests no basis to predict that this will change over the extended
time horizon.
A small number of shortfin mako sharks experience mortality as a
result of shark control/bather protection programs in South Africa and
Australia, which aim to reduce the risk of shark attacks on humans near
public beaches. Due to the localized geographic extent of the programs
and the very low number of individuals impacted, the ERA Team did not
find that shark control programs are likely contributing
[[Page 68263]]
to the extinction risk of the species now, and found it unlikely that
these programs would contribute significantly to extinction risk in the
foreseeable future as they defined it. We agree that the best available
scientific and commercial information indicates that these programs are
not likely contributing significantly to the species' extinction risk
now. Over the foreseeable future of 50 years that we have determined to
be more appropriate to apply for this species, we also find that bather
protection nets are not likely to significantly contribute to the
shortfin mako shark's risk of extinction because they are not currently
negatively affecting the species' status and the best available
scientific and commercial information suggests no basis to predict that
this will change over the extended time horizon.
In sum, the ERA Team did not identify any other natural or manmade
factors affecting the continued existence of the shortfin mako shark,
and we agree with their assessment.
Synergistic Impacts
We considered whether the impacts from threats described here and
in the Status Review Report may cumulatively or synergistically affect
the shortfin mako shark beyond the scope of each individual stressor.
As discussed previously, overutilization has resulted in historical
declines across the species' range and is expected to continue to
affect the species in certain regions over the foreseeable future. The
impact of overutilization on the species increases when regulatory
mechanisms to address this threat are inadequate. The species' low
productivity means that it will take longer to rebuild a stock if it
becomes depleted due to overutilization. While there is no evidence
that range contractions have occurred, or that destruction or
modification of shortfin mako shark habitat on a global scale has
occurred to such a point that it has impacted the status of the species
or is likely to in the foreseeable future, climate change has the
potential to alter the distribution of prey species and suitable
habitat that may result in changes in distribution. This may in turn
impact the frequency of fisheries interactions and resulting fishing
mortality. Further, climate change-induced shifts in the marine food
web have the potential to influence predation on juvenile shortfin mako
sharks over the next several decades. We cannot reasonably predict
either of these changes and their effects on the shortfin mako shark
based on the best available scientific and commercial information.
While some studies project that the species may be subject to
significant habitat loss by 2100, the shortfin mako shark's broad prey
base and thermal tolerance, among other factors, may give them a high
adaptive capacity (see the Status Review Report). The specific impacts
that climate change will have on the species, and how the species might
be able to adapt to changing oceanic conditions, is unknown. Therefore,
while we considered these potential synergistic effects, we conclude
that the best available scientific and commercial information indicates
that climate change is not likely to act synergistically with other
threats to increase the extinction risk of the shortfin mako shark now
or in the foreseeable future.
Extinction Risk Determination
Guided by the results and discussions from the demographic risk
analysis and ESA Section 4(a)(1) factor assessment, the ERA Team
analyzed the overall risk of extinction to the global shortfin mako
shark population. In this process, the ERA Team considered the best
available scientific and commercial information regarding the shortfin
mako shark from all regions of the species' global range, and analyzed
the collective condition of these populations to assess the species'
global extinction risk. The ERA Team was fairly confident in
determining the overall extinction risk of the species, placing two-
thirds of their likelihood points in the low risk category. Some
uncertainty was reflected in the allocation of points to the moderate
risk category, largely due to poor reporting of catches and low
confidence in abundance and trends in certain regions. No points were
allocated to the high risk category (see definitions of risk categories
in Methods).
The ERA Team acknowledged that the shortfin mako shark has
experienced historical declines of varying degrees in all ocean basins,
mainly due to interactions with commercial fishing vessels, however,
current abundance trends are mixed. A robust recent stock assessment in
the North Pacific indicates that the species is stable and potentially
increasing there, and population increases are also indicated in the
South Pacific. In other words, across the entire Pacific Ocean basin,
the species is either stable and/or potentially increasing. The recent
stock assessment in the North Atlantic, which the ERA Team also
considered highly reliable, indicates ongoing declines that will
continue into the foreseeable future. However, the ERA Team concluded
that this region is not at risk of extirpation based on available
projections carried out by ICCAT's SCRS, information on current
fisheries mortality, and predictions about future management and levels
of fisheries mortality. The South Atlantic may also have a declining
population trend, but this is highly uncertain. Fisheries mortality
remains high in the region. In the Indian Ocean, preliminary stock
assessments indicate that the shortfin mako shark population is
experiencing overfishing but is not overfished, and increasing CPUE
trends are indicated in several key fisheries in this region.
Compliance with reporting requirements is quite low in this region,
however, so the ERA Team felt that the extent of the species' decline
in this region is highly uncertain and potentially underestimated. Even
with continued declines in the North Atlantic and likely population
declines of uncertain degrees in the South Atlantic and Indian Oceans,
the stable and potentially increasing population status in the Pacific
Ocean, a major segment of the global population, led the majority of
the ERA Team to conclude that abundance would not contribute
significantly to the extinction risk of the species now or in the
foreseeable future. The ERA Team also concluded that the shortfin mako
shark's high genetic and ecological diversity, connectivity between
populations, and wide spatial distribution reduce the species'
extinction risk by providing resilience in the face of stochastic
events and threats concentrated in certain regions. The ERA Team did,
however, find that the low productivity of the species would likely
contribute significantly to the species' risk of extinction in the
foreseeable future as the species is highly susceptible to depletion
from exploitation, and will recover slowly from such declines.
Overutilization in commercial fisheries and inadequate regulatory
mechanisms to manage these fisheries are the main drivers of observed
population declines. While regulatory mechanisms have recently been
adopted to at least temporarily prohibit retention of the species in
the North Atlantic and to ensure the sustainability of the
international trade in shortfin mako shark products, it is too soon to
accurately assess the adequacy of these measures to address
overutilization. The ERA Team did consider the lack of compliance with
reporting requirements in the Indian Ocean and South Atlantic Ocean
concerning for the species, especially considering the high value of
the species in the meat and fin trade. The low confidence in catch data
also made it difficult for the ERA Team to assess whether regulatory
mechanisms
[[Page 68264]]
are inadequate to address the threat of overutilization in these
regions.
Overall, the ERA Team concluded that the species is not at high or
moderate risk of extinction based on the following: (1) the high
adaptability of the species based on its use of multiple habitat types,
tolerance of a wide range of water temperatures, and generalist diet;
(2) the existence of genetically and ecologically diverse, sufficiently
well-connected populations; (3) the species' wide spatial distribution
with no indication of range contractions or extirpations in any region,
even in areas where there is heavy bycatch mortality and utilization of
the species' high-value fins and meat; (4) the stable and potentially
increasing population trend indicated in the Pacific Ocean, a major
segment of the species' range; (5) abundance estimates of one million
and eight million individuals in the North Atlantic and North Pacific,
respectively; and (6) no indication that the species is experiencing
depensatory processes due to low abundance. Based on all of the
foregoing information, which represents the best scientific and
commercial data available regarding current demographic risks and
threats to the species, the ERA Team concluded that the shortfin
currently has a low risk of extinction rangewide.
We agree with the ERA Team's assessment that the shortfin mako
shark is not at high risk of extinction rangewide for the above
reasons. Extending the foreseeable future to 50 years (two generation
lengths), as we have determined is more appropriate to apply for this
species, does not alter this conclusion and, for the reasons summarized
here, we continue to find that the species is at low risk of extinction
throughout its range. In the North Atlantic, the population is
estimated to have experienced declines in total biomass of 47-60
percent and declines in SSF of 50 percent from 1950 to 2015 (ICCAT
2017). Since then, levels of fishing mortality in the North Atlantic
have declined in response to management measures implemented in recent
years (3,281 t in 2015; 3,356 t in 2016; 3,199 t in 2017; 2,373 t in
2018; 1,882 t in 2019; 1,709 t in 2020) (SCRS 2021). While we recognize
that current levels of mortality (1,709 t in 2020) are higher than any
of the TAC levels examined in the projections carried out by the SCRS
(up to 1,100 t inclusive of dead discards, ICCAT 2019), over the next
50 years, recently adopted retention prohibitions and increasing
international efforts to reduce the effects of fishing mortality on the
species in this region will likely result in further decreases in
fishing mortality in this region (although we are unable to conclude
the magnitude of potential declines, or whether they will be large
enough to rebuild the stock). Therefore, the best available scientific
and commercial information supports our forecast that the rate of
decline will likely slow compared to the 1950-2015 time period.
Although the stock is expected to decline until 2035 because the
immature sharks that have been depleted in the past will age into the
mature population over the next few decades, it is possible that the
stock may be able to begin to rebuild if fishing mortality is low
enough. Based on the above information, we find that future levels of
total fishing mortality are not likely to lead to extirpation of the
stock over the foreseeable future, even given estimates of historical
and recent population decline. In the South Atlantic, the status of the
shortfin mako shark is currently unclear. While it is probable that the
population is experiencing declines due to high fishing effort, current
stock status is highly uncertain, and it is difficult to predict the
magnitude of decline over the next 50 years. The South Pacific has an
increasing trend and there is no indication that this will change over
the next 50 years, although this trend is based on a shorter time
period, introducing some uncertainty into the future status of the
species in this region. In the North Pacific, the ISC Shark Working
Group stock assessment (2018) indicates that spawning abundances are
expected to increase gradually over a 10-year period (2017-2026) if
fishing mortality remains constant or is moderately decreased relative
to 2013-2015 levels. We take this to indicate that the current levels
of fishing mortality in this region are allowing the population to
grow, and there is no indication that this will change significantly in
the foreseeable future. In the Indian Ocean, it is difficult to
determine the stock status over the foreseeable future as current stock
status is highly uncertain, with declines potentially underestimated
due to poor reporting and data problems discussed above. The best
available scientific and commercial information for the species in this
region, including two preliminary stock assessments, indicates that the
species is undergoing overfishing but is not overfished, and recent
increasing CPUE trends are indicated in Spanish, Portuguese, and
Taiwanese longline fleets. Thus, although there is significant
uncertainty regarding the future status of this stock, and we
acknowledge that declines have been indicated, we conclude that the
species is not at risk of extirpation in this region over the next 50
years. In sum, although fishing mortality remains high throughout the
species' range and its low productivity life history does present a
concern for the species' risk of extinction over the foreseeable
future, we conclude on the basis of the best available scientific and
commercial data that the rangewide species is neither currently in
danger of extinction nor likely to become so within the foreseeable
future.
Significant Portion of Its Range
Under the ESA and our implementing regulations, a species may
warrant listing if it is in danger of extinction or likely to become so
within the foreseeable future throughout all or a significant portion
of its range. Having determined that the shortfin mako shark is not in
danger of extinction or likely to become so within the foreseeable
future throughout all of its range, we now consider whether the
shortfin mako shark is in danger of extinction or likely to become so
within the foreseeable future in a significant portion of its range--
that is, whether there is any portion of the species' range for which
it is true that both (1) the portion is significant; and (2) the
species, in that portion, is in danger of extinction or likely to
become so within the foreseeable future. A joint USFWS-NMFS policy,
finalized in 2014, provided the agencies' interpretation of this phrase
(``SPR Policy,'' 79 FR 37578, July 1, 2014) and explains that,
depending on the case, it might be more efficient for us to address the
``significance'' question or the ``status'' question first. Regardless
of which question we choose to address first, if we reach a negative
answer with respect to the first question, we do not need to evaluate
the other question for that portion of the species' range.
We note that the definition of ``significant'' in the SPR Policy
has been invalidated in two District Court cases that addressed listing
decisions made by the USFWS. The SPR Policy set out a biologically-
based definition that examined the contributions of the members in the
portion to the species as a whole, and established a specific threshold
(i.e., when the loss of the members in the portion would cause the
overall species to become threatened or endangered). The courts
invalidated the threshold component of the definition because it set
too high a standard. Specifically, the courts held that, under the
threshold in the policy, a species would never be listed based on the
status of the species in the portion, because in order for a portion to
meet
[[Page 68265]]
the threshold, the species would be threatened or endangered rangewide.
Center for Biological Diversity, et al. v. Jewell, 248 F. Supp. 3d 946,
958 (D. Ariz. 2017); Desert Survivors v. DOI 321 F. Supp. 3d. 1011
(N.D. Cal., 2018). However, those courts did not take issue with the
fundamental approach of evaluating significance in terms of the
biological significance of a particular portion of the range to the
overall species. NMFS did not rely on the definition of ``significant''
in the policy when making this 12-month finding. The ERA Team instead
chose to first address the question of the species' status in portions
of its range. While certain other aspects of the policy have also been
addressed by courts, the policy framework and key elements remain in
place, and until the policy is withdrawn we are bound to apply those
aspects of it that remain valid.
Because there are infinite ways to divide up the species' range for
an SPR analysis, the ERA Team only considered portions with a
reasonable likelihood of being both in danger of extinction or likely
to become so within the foreseeable future, and biologically
significant to the species. In asking the ``status'' question first,
the ERA Team considered whether the threats posed by overutilization
and inadequate regulatory measures are geographically concentrated in
any portion of the species' range at a biologically meaningful scale,
or whether these threats are having a greater impact on the status of
the species in any portions relative to other portions. While the
shortfin mako shark is subject to the threat of overutilization in
commercial fisheries across its range, fishing mortality is
substantially affecting the species in the North Atlantic Ocean, and is
projected to continue impacting the species' status in this region over
the next several decades. Because the North Atlantic stock of shortfin
mako shark is currently experiencing substantial negative effects of
overfishing and inadequate regulatory mechanisms (i.e., declines in SSF
of 50 percent from 1950 to 2015, as well as a 90 percent probability of
being overfished and experiencing overfishing), and will continue to be
impacted over the foreseeable future, the ERA Team concluded that there
was a reasonable likelihood that the species is at greater risk of
extinction in this portion relative to the remainder of the range and
determined to proceed to consider whether in fact the individuals in
that area were at moderate or high risk of extinction. The ERA Team
also considered whether the Atlantic Ocean as a whole is a portion that
may be at risk of extinction now or in the foreseeable future based on
indications of the species' decline in this portion, and to ensure a
thorough analysis of the species' status in this ocean basin.
Separate from the ERA Team, we (NMFS) went on to consider whether
other portions (the South Atlantic and the Indian Ocean) that were not
explicitly considered by the ERA Team had a reasonable likelihood of
being both in danger of extinction or likely to become so within the
foreseeable future, and biologically significant to the species. In the
South Atlantic, population declines of an unknown degree are likely
occurring, and fishing mortality remains high. The best available
scientific and commercial information indicates that the population has
only a 19 percent probability of being overfished and experiencing
overfishing, a 48 percent probability of not being overfished but
overfishing occurring, or alternatively, being overfished but
overfishing not occurring, and a 36 percent probability of not being
overfished or experiencing overfishing (ICCAT 2017). The 2017 stock
assessment of the population found conflicting results from different
models, resulting in high uncertainty. However, the stock assessment
notes that despite uncertainty, in recent years the stock may have been
at, or is already below, BMSY, and fishing mortality is
already exceeding FMSY. While the best available scientific
and commercial information leads us to find that high levels of fishing
mortality are likely leading to population declines in this region,
there is no indication that the resulting decline reflects that the
species in this portion has a reasonable likelihood of being in danger
of extinction or likely to become so within the foreseeable future.
Therefore, we did not consider the portion further. The best available
scientific and commercial information indicates that the shortfin mako
shark population in the Indian Ocean is considered to be experiencing
overfishing but is not yet overfished, and recent CPUE increases have
occurred in Spanish, Portuguese, and Taiwanese longline fleets.
Although population declines are potentially underestimated due to poor
reporting and data problems discussed previously, we do not have any
indication that the preliminary stock assessments available for this
region are invalid or suffer from methodological or other flaws that
would lead us to discount them. As the stock is not considered
overfished in either of these assessments, meaning that biomass has not
declined below the biomass at which the stock can produce maximum
sustainable yield on a continuing basis, we find it unlikely that
fishing mortality is impacting abundance to a degree that causes the
species to be at risk of extinction or likely to become so in the
foreseeable future in this portion of its range. Therefore, the best
available information does not support a conclusion that the species
has a reasonable likelihood of being at greater risk of extinction in
this portion relative to the remainder of the range, and the Indian
Ocean was not assessed further in the SPR analysis. Overutilization of
the species does not appear to be occurring in the Pacific Ocean: the
North Pacific population appears stable and is neither overfished nor
experiencing overfishing based on robust data, and the South Pacific
population has been indicated to be increasing with moderate certainty.
There is no indication that any region in the Pacific has a reasonable
likelihood of being in danger of extinction or likely to become so
within the foreseeable future, and therefore no portions in the Pacific
Ocean were considered further. The ERA Team therefore went on to assess
the extinction risk of two portions: the North Atlantic Ocean and the
Atlantic Ocean as a whole.
To determine extinction risk in each portion, the ERA Team used the
likelihood point method as described previously in Methods. The ERA
Team evaluated the best available information on the demographic
threats and ESA Section 4(a)(1) factors for shortfin mako sharks in
each portion, beginning with the North Atlantic Ocean portion. The
recent stock assessment conducted by ICCAT indicates that the North
Atlantic shortfin mako shark has experienced declines in biomass of
between 47-60 percent from 1950-2015, and predicts that SSF will
continue to decline until 2035 regardless of fishing mortality levels.
Despite the species' low productivity and the relatively high level of
fishing mortality impacting the species, the ERA Team concluded that
the species is not at high risk of extinction based on the current
abundance of the species in the portion (estimated at one million
individuals by FAO (2019)) and recent increased efforts to reduce
fishing mortality that are likely to be effective, at least to some
degree, in reducing the effect of overutilization on the species here.
Many of the ERA Team's points were placed in the moderate risk category
for the North Atlantic Ocean portion, which is reflective of the
species' low productivity and the considerable
[[Page 68266]]
uncertainty associated with potential effects of existing and future
regulatory mechanisms aimed at rebuilding and ending overfishing of the
North Atlantic shortfin mako stock over the next few decades (i.e.,
whether or not the resulting reduction in fishing mortality is
significant enough to end overfishing and begin to rebuild the
species). However, the ERA Team placed the majority of its likelihood
points in the low risk category and concluded that the North Atlantic
portion has a low extinction risk. Despite its continuing declining
trend, based on the best available scientific and commercial
information, the ERA Team did not conclude that the rate of decline in
the foreseeable future would be great enough to put the species in this
portion at high risk of extinction in the foreseeable future (see the
Status Review Report).
When conducting the analysis of the status of the species in the
Atlantic Ocean as a whole, the ERA Team considered the highly uncertain
fishing and abundance data available for the South Atlantic. Despite
this uncertainty, the best available scientific and commercial data
indicate that it is likely that the species' abundance in this region
is declining, with ICCAT's SCRS finding a 19 percent probability that
the stock is overfished and experiencing overfishing. The ERA Team also
considered the possible effects of the retention prohibition in the
North Atlantic and the potential for a shift in fishing effort for the
species to the South Atlantic. Overall, the ERA Team found that the
individuals of the species in the Atlantic Ocean portion as a whole
were not at high risk of extinction based on available abundance and
threats information. The ERA Team did place many points in the moderate
risk category to reflect the species' low productivity, and the
uncertainty in data and future regulatory mechanisms. However, the ERA
Team placed the majority of its points in the low risk category because
the level of fishing mortality and population decline expected within
the foreseeable future does not place the species in this portion at
high or moderate extinction risk in this timeframe.
Thus, to summarize, the ERA Team did not find the shortfin mako
shark to be in danger of extinction or likely to become so within the
foreseeable future in either of these portions of its range. As a
result, the ERA Team did not continue the analysis to evaluate whether
either of these portions constitutes a biologically significant portion
of the shortfin mako shark's range.
We agree with the ERA Team's conclusions that the species is not in
danger of extinction now within the North Atlantic or the Atlantic
Ocean as a whole. When we extended the foreseeable future to 50 years,
which we have determined is more appropriate to apply for this species,
we also reached the same conclusion as the ERA Team. The North Atlantic
shortfin mako shark population is estimated to have experienced
declines in total biomass of 47-60 percent and declines in SSF of 50
percent from 1950 to 2015 (ICCAT 2017). Since then, levels of fishing
mortality in the North Atlantic have declined in response to management
measures implemented in recent years (3,281 t in 2015; 3,356 t in 2016;
3,199 t in 2017; 2,373 t in 2018; 1,882 t in 2019; 1,709 t in 2020)
(SCRS 2021). While we recognize that current levels of mortality (1,709
t in 2020) are higher than any of the TAC levels examined in the
projections carried out by the SCRS (up to 1,100 t inclusive of dead
discards, ICCAT 2019), over the next 50 years, recently adopted
retention prohibitions and increasing international efforts to reduce
the effects of fishing mortality on the species in this region will
likely result in further decreasing levels of fishing mortality in this
region (although we are unable to conclude the magnitude of potential
declines, or whether they will be large enough to rebuild the stock).
Therefore, the best available scientific and commercial information
supports our forecast that the rate of decline will likely slow
compared to the 1950-2015 time period. Although the stock is expected
to decline until 2035 because the immature sharks that have been
depleted in the past will age into the mature population over the next
few decades, it is possible that the stock may be able to begin to
rebuild if fishing mortality is low enough. We find that future levels
of fishing mortality are not likely to place the species in danger of
extinction in the foreseeable future within this portion, even given
estimates of historical and recent decline. In the South Atlantic, it
is likely that the population is experiencing decline of an unknown
degree due to continued high fishing effort and mortality. Results of
the 2017 stock assessment indicate a 19 percent probability that the
stock is overfished and experiencing overfishing, with conflicting
results from different models used. Current stock status is highly
uncertain, and it is therefore difficult to predict the magnitude of
decline over the next 50 years. However, the greater abundance, habitat
area, spatial distribution, and ecological diversity of the North and
South Atlantic populations together as a portion provide additional
resilience that makes extinction less likely. Therefore, we do not find
that the Atlantic portion is likely to be in danger of extinction in
the foreseeable future. Because we did not find the shortfin mako shark
to be in danger of extinction or likely to become so within the
foreseeable future in either of these portions, and because to support
a listing on the basis of SPR the individuals in a portion would need
to both have a threatened or endangered status and be biologically
significant to the overall species, we did not consider whether these
portions qualify as significant portions of the shortfin mako shark's
range.
Distinct Population Segments
The petition to list the shortfin mako shark requested that NMFS
list the species throughout its range, or alternatively, as DPSs, in
the event that NMFS concludes that they exist. Therefore, we examined
the best available information to determine whether DPSs may exist for
this species. The petition did not provide information regarding
potential DPSs of shortfin mako shark.
As discussed previously, the DPS Policy provides guidelines for
defining DPSs and identifies two elements to consider in a decision
regarding whether a population qualifies as a DPS: discreteness and
significance of the population segment to the species (61 FR 4722;
February 7, 1996). A population may be considered discrete if it is
markedly separate from other populations of the same taxon as a
consequence of physical, physiological, ecological, or behavioral
factors, or if it is delimited by international governmental
boundaries. Genetic differences between the population segments being
considered may be used to evaluate discreteness. If a population
segment is considered discrete, its biological and ecological
significance must then be evaluated. Significance is evaluated in terms
of the importance of the population segment to the overall welfare of
the species. Some of the considerations that can be used to determine a
discrete population segment's significance to the taxon as a whole
include: (1) persistence of the population segment in an unusual or
unique ecological setting; (2) evidence that loss of the population
segment would result in a significant gap in the range of the taxon;
and (3) evidence that the population segment differs markedly from
other populations of the species in its genetic characteristics.
[[Page 68267]]
To determine whether any discrete populations of shortfin mako
sharks exist, we looked at available information on shortfin mako shark
population structure, including tagging, tracking, and genetic studies.
As discussed previously in Habitat Use and Population Structure and
Genetics, although certain ocean currents and features may limit
movement patterns between different regions, available genetic studies
indicate a globally panmictic population with some genetic structuring
among ocean basins.
Heist et al. (1996) investigated genetic population structure using
restriction fragment length polymorphism analysis of maternally
inherited mtDNA from shortfin mako sharks in the North Atlantic, South
Atlantic, North Pacific, and South Pacific. The North Atlantic samples
showed significant isolation from other regions (p <0.001), and
differed from other regions by the relative lack of rare and unique
haplotypes, and high abundance of a single haplotype (Heist et al.
1996). Reanalysis of the data found significant differentiation between
the South Atlantic and North Pacific samples (Schrey and Heist 2003) in
addition to isolation of the North Atlantic.
A microsatellite analysis of samples from the North Atlantic, South
Atlantic (Brazil), North Pacific, South Pacific, and Atlantic and
Indian coasts of South Africa found very weak evidence of population
structure (FST = 0.0014, P = 0.1292; RST =
0.0029, P = 0.019) (Schrey and Heist 2003). These results were
insufficient to reject the null hypothesis of a single genetic stock of
shortfin mako shark, suggesting that there is sufficient movement of
shortfin mako sharks, and therefore gene flow, to reduce genetic
differentiation between regions (Schrey and Heist 2003). The authors
note that their findings conflict with the significant genetic
structure revealed through mtDNA analysis by Heist et al. (1996). They
suggest that as mtDNA is maternally inherited and nuclear DNA is
inherited from both parents, population structure shown by mtDNA data
could indicate that female shortfin mako sharks exhibit limited
dispersal and philopatry to parturition sites, while male dispersal
allows for gene flow that would explain the results from the
microsatellite data (Schrey and Heist 2003).
Taguchi et al. (2011) analyzed mtDNA samples from the North and
South Pacific, North Atlantic, and Indian Oceans, finding evidence of
significant differentiation between the North Atlantic and the Central
North Pacific and Eastern South Pacific (pairwise [Phi]ST =
0.2526 and 0.3237, respectively). Interestingly, significant structure
was found between the eastern Indian Ocean and the Pacific Ocean
samples (pairwise [Phi]ST values for Central North Pacific,
Western South Pacific, Eastern South Pacific are 0.2748, 0.1401, and
0.3721, respectively), but not between the eastern Indian and the North
Atlantic.
Corrigan et al. (2018) also found evidence of matrilineal structure
from mtDNA data, while nuclear DNA data provide support for a globally
panmictic population. Although there was no evidence of haplotype
partitioning by region and most haplotypes were found across many
(sometimes disparate) locations, Northern Hemisphere sampling locations
were significantly differentiated from all other samples, suggesting
reduced matrilineal gene flow across the equator (Corrigan et al.
2018). The only significant differentiation indicated by microsatellite
data was between South Africa and southern Australia (pairwise
FST = 0.037, [Phi]ST = 0.043) (Corrigan et al.
2018). Clustering analysis showed only minor differences in allele
frequencies across regions, and little evidence of population structure
(Corrigan et al. 2018). Overall, the authors conclude that although
spatial partitioning exists, the shortfin mako shark is genetically
homogenous at a large geographic scale.
Taken together, results of genetic analyses suggest that female
shortfin mako sharks exhibit fidelity to ocean basins, possibly to
utilize familiar pupping and rearing grounds, while males move across
the world's oceans and mate with females from various basins (Heist et
al. 1996; Schrey and Heist 2003; Taguchi et al. 2011; Corrigan et al.
2018). This finding does not support the existence of discrete
population segments of shortfin mako sharks.
We also considered whether available tracking data support the
existence of discrete population segments of shortfin mako shark. There
is some evidence that certain ocean currents and features may limit
movement patterns, including the Mid-Atlantic ridge separating the
western and eastern North Atlantic, and the Gulf Stream separating the
North Atlantic and the Gulf of Mexico/Caribbean Sea (Casey and Kohler
1992; Vaudo et al. 2017; Santos et al. 2020). However, conventional
tagging data indicates that movement does occur across these features
(Kohler and Turner 2019). In the Pacific, tagging data supports east-
west mixing in the north and minimal east-west mixing in the south
(Sippel et al. 2016; Corrigan et al. 2018). Trans-equatorial movement
may be uncommon based on some tagging studies, though tagged shortfin
mako sharks have been recorded crossing the equator (Sippel et al.
2016; Corrigan et al. 2018; Santos et al. 2021). Therefore, we conclude
that there do not appear to be major barriers to the species' dispersal
that would result in marked separation between populations.
Overall, we find that the best available scientific and commercial
information does not support the existence of discrete populations of
shortfin mako shark. Because both standards, of discreteness and
significance, have to be met in order to conclude that a population
would constitute a DPS, we conclude that there are no population
segments of the shortfin mako shark that would qualify as a DPS under
the DPS Policy.
Final Listing Determination
Section 4(b)(1) of the ESA requires that NMFS make listing
determinations based solely on the best scientific and commercial data
available after conducting a review of the status of the species and
taking into account those efforts, if any, being made by any state or
foreign nation, or political subdivisions thereof, to protect and
conserve the species. We relied on available literature and information
from relevant countries to evaluate efforts to protect and conserve the
species, including National Plans of Action for the Conservation and
Management of Sharks (NPOA-Sharks), which are developed under the IPOA-
SHARKS and aim to ensure the conservation, management, and long-term
sustainable use of sharks. While the development of NPOAs provide some
indication of the level of commitment of a catching country to manage
its shark fisheries and provides a benefit to sharks, the quality of
existing NPOA-Sharks varies, and there are no reporting mechanisms on
implementation of the NPOAs; thus, it remains uncertain whether a
particular plan is being implemented or what impact the plan has had on
conservation and management of sharks. These conservation efforts do
not change the conclusion we would otherwise have reached regarding the
species' status. We have independently reviewed the best available
scientific and commercial information, including the petitions, public
comments submitted in response to the 90-day finding (86 FR 19863;
April 15, 2021), the Status Review Report, and other published and
unpublished information. We considered each of the statutory factors to
determine whether each contributed significantly to the extinction risk
of the species. As required by the ESA, section 4(b)(1)(a), we also
took into account
[[Page 68268]]
efforts to protect shortfin mako sharks by states, foreign nations, or
political subdivisions thereof, and evaluated whether those efforts
provide a conservation benefit to the species. As previously explained,
we could not identify a significant portion of the species' range that
is threatened or endangered, nor did we find that any DPSs of the
species exist. Therefore, our determination is based on a synthesis and
integration of the foregoing information, factors and considerations,
and their effects on the status of the species throughout its entire
range.
We have determined the shortfin mako shark is not presently in
danger of extinction, nor is it likely to become so in the foreseeable
future throughout all or a significant portion of its range. This
finding is consistent with the statute's requirement to base our
findings on the best scientific and commercial data available,
summarized and analyzed above. Therefore, the shortfin mako shark does
not meet the definition of a threatened species or an endangered
species and does not warrant listing as threatened or endangered at
this time.
This is a final action, and, therefore, we are not soliciting
public comments.
References
A complete list of the references used in this 12-month finding is
available online (see ADDRESSES) and upon request (see FOR FURTHER
INFORMATION CONTACT).
Peer Review
In December 2004, the Office of Management and Budget (OMB) issued
a Final Information Quality Bulletin for Peer Review establishing
minimum peer review standards, a transparent process for public
disclosure of peer review planning, and opportunities for public
participation. The OMB Bulletin, implemented under the Information
Quality Act (Pub. L. 106-554) is intended to enhance the quality and
credibility of the Federal Government's scientific information, and
applies to influential or highly influential scientific information
disseminated on or after June 16, 2005. To satisfy our requirements
under the OMB Bulletin, we obtained independent peer review of the
Status Review Report. Three independent specialists were selected from
the academic and scientific community for this review. All peer
reviewer comments were addressed prior to dissemination of the final
Status Review Report and publication of this 12-month finding. The Peer
Review Report can be found online at: https://www.noaa.gov/information-technology/endangered-species-act-status-review-report-shortfin-mako-shark-isurus-oxyrinchus-id430.
Authority: The authority for this action is the Endangered Species
Act of 1973, as amended (16 U.S.C. 1531 et seq.).
Dated: November 4, 2022.
Samuel D. Rauch, III,
Deputy Assistant Administrator for Regulatory Programs, National Marine
Fisheries Service.
[FR Doc. 2022-24493 Filed 11-10-22; 8:45 am]
BILLING CODE 3510-22-P