Monitoring of fishes and invertebrates at Tijuana Estuary

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NOAA Technical Memorandum

NOS MEMD 10

MONITORING OF FISHES AND INVERTEBRATES

AT TIJUANA ESTUARY
[ r- op. T'-
Christopher S. Nordby

Pacific Estuarine Research Laboratory, Biology Department,
San Diego State University, San Diego, CA 92182-0057

U.S. DEPARTMEN'r OF COMMERCE NOAA
COASiAL $!FP',Cr E.ENTER
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Washington, D.C.
August 1987

UNITED STATES National Ociault and National ocean Service 9
OEPARTMENT OF COMMERCE Atmotsphertc Administratio n

_ /

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be preliminary in nature and may be published in other referreed journals at a later date.

MEMD 1 M.M. Littler, D.S. Littler and B.E. Lapointe. 1986. Baseline Studies of Herbivory and Eutrophication
on Dominant Reef Communities of Looe Key National Marine Sanctuary.

MEMD 2 M.M. Croom and N. Stone, Eds. 1987. Current Research Topics in the Marine Environment.

MEMD 3 C.E. Birkeland, R.H. Randall, R.C. Wass, B. Smith, and S. Wilkens. 1987. Biological Resource
Assessment of the Fagatele Bay National Marine Sanctuary

MEMD 4 H. Huber. 1987. Reproduction in Northern Sea Lions on Southeast Farallon Island, 1973-1985.

MEMD 5 J.A. Bohnsack, D.E. Harper, D.B. McClellan, D.L. Sutherland, and M.W. White. 1987. Resource
Survey of Fishes within Looe Key National Marine Sanctuary.

MEMD 6 S.G. Allen, D.G. Ainley, L. Fancher, and D. Shuford. 1987. Movement Patterns of Harbor
Seals (Phoca vitulina) from the Drakes Estero Population, California, 1985-86.

MEMD 7 S.G. Allen. 1987. Pinniped Assessment in Point Reyes, California, 1983 to 1984.

MEMD 8 G.H. Han, R.W. Calvert, J.O. Blanton. 1987. Current Velocity Measurements at Gray's Reef National
Marine Sanctuary.

MEMD 9 B.E. Lapointe and N.P. Smith. 1987. A Preliminary Investigation of Upwelling as a Source of
Nutrients to Looe Key National Marine Sanctuary.

MEMD 10 C.S. Nordby. 1987. Monitoring of Fishes and Invertebrates at Tjuana Estuary.

National Marine Sanctuary Program
Marine and Estuarine Management Division
Office of Ocean and Coastal Resource Management
National Ocean Service
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NOTE TO READERS

On April 7, 1987, the Congress of the United States amended Section 315 of the Coastal Zone Management Act to
establish the National Estuarine Reserve Research System (P.L. 99-272). Formerly known as the National Estuarine
Sanctuary Program, each national estuarine sanctuary established prior to this date was automatically made part of
the new system and designated a national estuarine research reserve. The new System emphasizes the research
value of each site since they are areas representative of estuarine ecosystems that are suitable for long-term research
and contribute to the biogeographical and typological balance of the System.

REPORT TO
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
U.S. DEPARTMENT OF COMMERCE

NOAA TECHNICAL MEMORANDA SERIES NOS/MEMD

Monitoring of Fishes and Invertebrates at Tijuana Estuary

Christopher S. Nordby

August 1987

U.S. DEPARTMENT OF COMMERCE
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
NATIONAL OCEAN SERVICE
OFFICE OF OCEAN AND COASTAL RESOURCE MANAGEMENT
MARINE AND ESTUARINE MANAGEMENT DIVISION
WASHINGTON, D.C.

REPORT TO
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
U.S. DEPARTMENT OF COMMERCE

NOAA TECHNICAL MEMORANDA SERIES NOS/MEMD

Monitoring of Fishes and Invertebrates at Tijuana Estuary

Christopher S. Nordby

Pacific Estuarine Research Laboratory, Biology Department,
San Diego State University, San Diego, CA 92182-0057

This work is the result of research sponsored by the U.S.
Department of Commerce, National Oceanic and Atmospheric
Administration, National Ocean Service, Office of Ocean and
Coastal Resource Management, Marine and Estuarine Management Division
Under Contract Number NA-86-AA-D-CZ016

Table of Contents

Abstract

Introduction ..........................

Methods ............................

Results and Discussion....................3

Conclusions .........................9

Recommendations .......................10

Acknowledgements ........................

Literature Cited.......................12

List of Tables

1. Taxonomic composition, relative abundance and densities of adult
and juvenile fishes collected at 5 sampling sites at Tijuana
Estuary, CA.
2. Physical conditions of S sampling sites at Tijuana Estuary, CA.
3a. Comparison of adult and juvenile fishes and ichthyoplankton
collected from Station E1 on consecutive days.
3b. Comparison of adult and juvenile fishes collected from Station E2
on consecutive days.
4. Halibut gut analysis.
S. Taxonomic composition, number collected and mean density per
sample of fish and larvae collected at 3 sampling sites at Tijuana
Estuary, CA.
6. Mean densities of zooplankton collected from 3 sampling stations
at Tijuana Estuary July 22 through August 4, 1986.
7. Benthic invertebrates collected from 5 sampling sites at Tijuana
Estuary, CA.
8. Bivalves collected from S main channel sampling sites at Tijuana
Estuary, CA.
9. Densities of dominant bivalves collected from 5 main channel sites
at Tijuana Estuary during September, 1986 and January, 1987.
10. Benthic invertebrates collected from areas impacted by
sedimentation from dune wash-over and adjacent sites not impacted.
11. Mean densities of bivalves collected at a dredged and non-dredged
area of southern channel at Tijuana Estuary, CA.

List of Figures

1. Sampling stations at Tijuana Estuary, CA.
2. Species diversity of adult and juvenile fishes collected on 4
dates at Tijuana Estuary, CA in 1986-87.
3. Species diversity of adult and juvenile fishes collected from 5
sites at Tijuana Estuary, CA in 1986-87.
4a. Catch per unit effort of adult and juvenile fishes at station E2
on 3/10/87.
4b. Catch per unit effort of adult and juvenile fishes at station E2
on 3/11/87.
Sa. Species composition of repeated seinings at station E2 on 3/10/87.
5b. Species composition of repeated seinings at station E2 on 3/11/87.
6. Size frequency analysis of Topsmelt at station El.
7. Size frequency analysis of Topsmelt at station E2.
8. Size frequency analysis of California halibut at station E2.

Abstract

Fishes and benthic invertebrates responded differently to the impacts of
elevated water salinities and temperatures due to closure of the estuary
mouth; sedimentation as the result of dune sand deposition in estuarine
channels; and, dredging to remove those sediments. Increased salinities
resulted in the mortality of all benthic invertebrates except spionid
worms. California halibut (Paralichthys californicus), Diamond turbot
(Rypsopsetta guttulata), and Pacific staghorn sculpin (Leptocottus armatus)
were not encountered at salinities higher than 50ppt, while Longjaw
mudsucker (Gillichthys mirabilis) survived salinities as high as lOOppt but
showed a lag response to increased salinities with populations declining in
1986-87. Benthic invertebrates demonstrated an immediate response to
sedimentation while fish response was unclear. The dominant bivalves were
eliminated and levels of polychaete worms drastically reduced by such
events. While fish diversity and density were lower following
sedimentation events, it could not be determined whether this response was
due to avoidance of the area or mortality. Dredging to remove sediments
resulted in the coincidental removal and mortality of benthic
invertebrates.
Populations of both fish and invertebrates were dominated by small size
classes, suggesting recruitment from oceanic sources. Due to the skewed
distribution of size classes, the system is not stable in terms of
population biology, and is susceptible to further physical fluctuations.
It is recommended that such fluctuations be avoided by maintenance of tidal
flushing and increasing tidal prism, despite the initial impacts to the
channel biota.

Introduction

Tijuana Estuary, designated a National Estuarine Research Reserve by NOAA
OCRM in 1982, is a small coastal wetland containing approximately 60ha of
channels at high tide and 200ha of associated salt marsh (McIllwee 1970). A
narrow barrier dune separates the main channels of the estuary from the Pacific
Ocean (Figure 1). In January 1983, concurrent high tides and heavy surf washed
dune sand into the main estuary channel, substantially reducing the tidal prism
and ultimately causing the closure of the estuary mouth to tidal flushing.
Closure occurred in early April, 1984, and tidal flushing was reinstated in
December 1984. During this period precipitation was near zero and channel
salinities rose to over lOOppt, eliminating the marine dominated channel biota.

The purpose of this study was to assess the effects of mouth closure and
sedimentation on the system and monitor population dynamics of fishes and
invertebrates following the reinstatement of tidal flushing and dredging to
remove sediments. Adult and juvenile fishes, ichthyoplankton, and benthic
invertebrates were monitored quarterly at 3-5 sites, depending upon season
(Figure 1). In addition, the examination of summer zooplankton populations,
extensive monitoring of bivalve populations, analysis of sampling efficiency,
and gut analysis of juvenile halibut were conducted. In January 1, 1987, high
tides again washed dune sand into the estuarine channels providing a natural
experiment on the short-term effects of sedimentation on channel organisms.

Methods

Sampling Stations

Sampling sites were chosen on the basis of channel morphometry, a
multi-factor parameter that describes channel depth, substrate composition,
position relative to the mouth of the estuary, and bank slope. Station El was
located in the main north-south channel of the estuary (Figure 1). The width
and depth at this site varied from 13m to 14m and from .am to .75m,
respectively, depending upon tidal height. The eastern bank was sharply eroded
while the western bank was gradual and depositional. Substrate was composed
primarily of sand with some mud. Station E2 was located in a dredged channel
situated east-west and connecting the inland lagoon with the main north-south
channel. This site was 12m wide and depth varied from .3m to im. Banks were
sharply eroded and substrate consisted of clay and shell fragments. Site E3 was
a channel near the mouth of the estuary approximately lOm wide and .3m to .Sm
deep. The banks were gently sloped and substrate was sand/mud. Site E4 was a
tidal creek corresponding to Net Creek of Nordby (1982). The width at E4 was 2m
while depth varied from .5m to Im. Banks sloped abruptly and substrate was fine
mud. ES, another tidal creek, was sampled one time only in fall 1986 when the
water level in E4 was too low to sample. This creek was 2m wide and Is deep
with gently sloping banks and fine mud substrate. Tidal creek habitats were
intertidal, draining completely on lower tides. Thus, stressful conditions
limited benthic invertebrate populations to various gastropods and polychaetes.

It was originally proposed that riverine channels, gravel pit ponds and

intertidal ponds be sampled as well as main channels and tidal creeks. However,
after the initial sampling period, these sites were omitted due to lack of
useful information. For example, gravel pit ponds yielded only one (non-native)
fish species (Mosquitofish, Gambusia affinis) while riverine channels proved too
shallow to seine. Thus sampling stations were concentrated in the main channels
and tidal creeks of the estuary.

Adult and Juvenile Fishes

Adult and juvenile fishes were collected using a 3mm mesh bag seine and two
3mm mesh blocking nets. The blocking nets were deployed at slack low tide to
block a section of channel and contain fishes within that area. Repeated seines
were hauled through the area until the number of fish captured per seine
approached zero. The blocking nets were then closed by sweeping in toward the
center of the blocked area. Sampling efficiency was tested by using the catch
per unit effort method, where the number of fish caught is plotted against prior
cumulative catch. This method compares the estimated total number of fish within
the blocked portion of the channel with the actual number caught. In addition,
the species composition of fishes captured in each repeated seine was compared
to demonstrate the species selectivity of the sampling gear.

Ichthyoplankton

Fish eggs and larvae were collected at stations El, �2, and �3 using three
30-cm diameter plankton nets of 505 micron mesh (Nitex nylon screen) with center
mounted flow meters to estimate the volume sampled. Nets were deployed on the
flood tide, 1.5 hour prior to high slack tide, and on the ebb tide 1 hour after
high slack tide. Sampling was conducted for one hour, after which nets were
removed, cleaned, and samples preserved in 3% formalin buffered with seawater.

It was proposed that ichthyoplankton be collected on both flood and ebb
tides on each sampling date to determine the role of tidal transportation as the
primary mechanism controlling ichthyoplankton distribution within the estuary,
as hypothesized by Nordby (1982). However, due to reduced tidal circulation as
a result of channel sedimentation, tidal cycles were unpredictable and often
disrupted. Thus, only one tide, either ebb or flood, was usually sampled on a
given date.

Benthic Invertebrates

Benthic infaunal invertebrates were sampled using a 15cm diameter "clam
gun" as a coring device. This device was pressed into the substrate to a depth
of 20cm and the core of sediment screened through a lmm mesh sieve. All large
animals were identified in the field and released. Smaller, unidentified
organisms were fixed in 3N formalin buffered with seawater and taken to the
laboratory for examination.

Invertebrates were sampled using two approaches: cores were taken in the
areas blocked for adult and juvenile fish collection and concentrated sampling
was conducted in areas where fishes were not sampled (Figure 1).

Zooplankton

Although not originally proposed for the monitoring program, the summer

zooplankton populations within the main channels of Tijuana Estuary were
examined by N. Hellberg, SDSU-U.C. Davis joint doctoral student. Collections
were taken simultaneously with ichthyoplankton samples.

Results and Discussion

Adult and Juvenile Fishes

A total of 20 species of fish from 14 families was collected (Table 1).
Dominant species include Topsmelt (Atherinopa affinia), Arrow goby (Clevelandia
ioa), Pacific staghorn sculpin (Leptocottus armatua), and California killifish
(Fundulus narvipinnis), all of which are generally regarded as resident
estuarine species.

On a seasonal scale, species diversity was highest in spring and summer
when 13 and 14 species, respectively, were collected and lowest in fall and
winter when 9 species were taken during each sampling period (Figure 2).

Spatially, diversity was highest at station El (15 species) followed by E2
(14 species) and E3 (10 species) (Figure 3). Tidal creeks contained the lowest
number of species with the combined total of 4 species at sites E4 and ES.

Densities of the dominant species were variable but some general patterns
are evident (Table 1). Topamelt were collected in high densities at all sites
except E5, which was sampled on one date only (I1/25/86) when tidal levels at
site E4 were too low to allow seining. This is a highly mobile species that
forms schools and utilizes the entire water column. Thus, it is difficult to
correlate physical variables such as substrate and water chemistry with the
distribution and abundance of this species.

The distribution and abundance of the other dominant species appear to be
related to substrate type and other characteristics of channel morphometry -
water depth, tidal velocity, and distance to the mouth of the estuary - and with
the availability of food. Arrow goby densities were always highest at E3, the
station closest to the mouth of the estuary. The channel at this site is
shallow, with low tidal velocity and a sand/mud substrate. These physical
characteristics make E3 a site conducive to burrow construction and maintenance
by goby species (Brothers 1975). Arrow gobies greater than 14sm are benthic
carnivores and feed primarily on cyclopoids, ostracods, nematodes, oligochaetes
and harpacticoids (MacDonald 1975). The distribution and abundance of benthic
invertebrates and zooplankton in Tijuana Estuary are presented in later sections
of this report. However, sites E3 and E4, which contained the highest densities
of Arrow gobies, contained abundant zooplankton and benthic worms. The
association of Arrow gobies with commensal organisms such as Ghost shrimp
(Callianassa californiensis) is well documented (Brothers 1975). Ghost shrimp
burrows were abundant at both sites.

The high densities of gobies encountered at station E3 may help to explain
the high numbers of gobiid larvae collected in plankton tows from nearshore
waters adjacent to Tijuana Estuary in 1980-81 (Nordby 1982). A spawning event
near the mouth would result in the tidal translocation of larvae to the
nearshore habitat.

Pacific staghorn sculpin, which were abundant only during the spring and
summer, occurred primarily in sandy substrate (El) and sandy/mud (E3), although

numerous small individuals were collected from E2 during March, 1987. This
species feeds mainly on decapod crustaceans such as Ghost shrimp and Yellow
shorecrab (Hemiqrsasus oregonensis) (Tasto 1975). Ghost shrimp were abundant at
both E1 and E3, while Yellow shorecrabs were common throughout the estuary.

Topamelt greater than 34mm feed primarily on green algae, such as
Enteromorpha ap. (Allen 1980). These algae are most abundant in Tijuana Estuary
in late winter-early spring (Rudnicki 1986)and occur in greatest abundance in
low tidal velocity channels. All of the sites sampled in this study supported
periodic blooms of these algae.

The Longjaw mudaucker (Gillichthys mirabilis) is considered a resident
estuarine species that preys upon and inhabits the burrows of larger crab
species, such as the Yellow shorecrab. Despite the abundance of prey organisms,
populations of Longjaw mudauckers were very low at Tijuana Estuary during this
study, relative to populations prior to and during closure to tidal flushing.
Prior to closure, Longjaw mudsuckers were abundant in the tidal creeks of the
estuary (Nordby, pers. obs.). Although comparable data from seining operations
are not available, Longjaw mudsuckers were taken using minnow traps in 1979-80
(Nordby, unpub. data). Indirect evidence of the abundance of this species in the
system prior to 1984 is demonstrated in the ichthyoplankton collections of
Nordby (1982). Long3aws comprised 29x of the total larvae collected in main
channels (3,878) and 79X (684) of those collected from a tidal creek using a
channel net method (Nordby 1982).

During closure, an SDSU Estuarine Ecology class sampled seven sites within
Tijuana Estuary. Longjaw mudauckers were present at 2 main channel sites,
corresponding roughly to El, and in the east-west channel corresponding to E2.
Channel salinities at this time were about 60 ppt. Although not numerous
(Longjaws accounted for about 4x of the catch, or 22 of 575 fishes), they were
widespread and relatively large, ranging from 77smm to 113mm. Thus, adults of
this species can tolerate salinities of 60ppt. Whether or not they can spawn
under such conditions is unknown. Salinities then rose to around lOOppt before
reintroduction of tidal flushing.

In the current study, Longjaws were collected at only two sites on two
dates (Table 1). Thirty-nine individuals were collected from E2 in August,
while 2 individuals were taken from E3 in March. This low relative abundance
suggests a lag effect of increased salinity. Although adults are present in the
system, population levels are apparently so low that recovery will take several
spawning seasons. The data from ichthyoplankton collections (see next section)
demonstrate the low recruitment potential of this species in 1986-87.

Additional support for the salinity-induced population decline is provided
by the results of a similar monitoring program at Los Penasquitos Lagoon (ERA
1987), an occasionally flushed lagoon approximately 40 miles north of Tijuana
Estuary, and from spring 1987 sampling conducted at Bahia de San Quintin, a
relatively pristine wetland located approximately 150 miles south of Tijuana
Estuary in Baja, Mexico (Nordby unpub. data). Although Los Penasquitos Lagoon
was closed to tidal flushing for much of 1986-87, Longjaw mudsuckers were the
third most abundant species taken in this system, comprising 4.1X of the total
catch, or 170 individuals. Although methods and net meshes were not comparable,
a pattern of salinity and abundance can be demonstrated. Salinities during this
period did not rise above 50ppt (range = Oppt to 50ppt). At Bahia de San
Quintin, two tidal creeks were sampled for fishes using the same methods as the

present study. Long3aw mudauckers comprised 438 (40) of the total caught at
creek 1, and comprised 9OX (72) of the total at creek 2. Salinities were 45ppt
and S0ppt, respectively. Thus, populations can tolerate relatively high
salinities but not extreme salinities such as lOOppt.

Other species showed similar responses to salinity. Samples collected at
Ti uana Estuary during closure conditions lacked the common Staghorn sculpin,
California halibut (Paralichthys californicus) and Diamond turbot (Hypsopsetta
guttulata). These species were present in tidal creek I at Bahia de San Ouintin
where salinity was 45ppt, but were absent from tidal creek 2 where salinity was
50ppt. Thus, salinities greater than 50ppt appear to exceed the tolerance of
several estuarine species.

Physical conditions during the present study were relatively stable (Table
2) with salinities ranging from 32ppt to 38ppt, temperature from 15 to 29C,
and dissolved oxygen from 2ppm to saturated levels. There was little
correlation between physical factors and fish distribution and abundance (Table
1). Tidal flushing was maintained throughout the 1986-87 sampling year,
although at reduced levels due to sedimentation.

Test of Sampling Efficiency

In order to estimate population size and determine how many fish within the
blocked area of the channel were actually captured, the following exercise was
conducted at site E2 on March 10, 1987, and again on March 11, 1987: Repeated
seines were drawn through the blocked area until the number of fish caught
approached zero. Then, the two blocking nets were "closed" by pulling each
toward the center of the blocked area. The total number of fish within the
blocked area was calculated using the catch per unit effort method where the
number caught is plotted against the prior cumulative catch (Figures 4a and 4b).
The selectivity of the gear for various species was examined by plotting number
caught in each repeated seine (Figures Sa and 5b).

As demonstrated by the catch per unit effort, five repeated seines and the
two closing nets are necessary to adequately sample the fishes in the blocked
channel. The sampling gear and the "catchability" of each species is similar in
both cases. On March 10, 96% of the Topsmelt were taken in the first tow while
on March 11, 69% of this species were captured in the first tow. Benthic fishes
such as the dominant Arrow gobies comprised relatively few of the initial seine
but were taken in increasingly higher numbers on the second and third tows
before declining.

The two consecutive sampling dates also allow for a comparison of daily
variation in the fish communities. This comparison was made because the high
degree of daily and weekly variation in some systems renders seasonal
comparisons meaningless. A similar test was conducted at site El on November 25
and November 26, 1986. Species composition was very similar at both sites for
each comparison (Tables 3a and 3b). These results suggest that comparisons
based on seasonal sampling are valid.

Size Frequency Analysis

Size frequency data for selected species (Figures 6-8) are included to show
changes in various populations through time. Topamelt collected from stations
El and E2 demonstrated similar temporal patterns. Collections in spring were

composed of two distinct size classes dominated numerically by smaller ( 40mm)
fish with fewer large ( >)100mm) individuals. These appear to represent the year
1 recruits and spawning adults, respectively. Summer collections were typified
by larger, yet fewer, young of the year (around 50mm in length) and an absence
of adults. While less clear at station El, the collections from E2 in the fall
show a bimodal distribution with the majority of those collected falling into
the 100mm size with a second peak around 150 mm. These may be interpreted as
the maturing year 1 recruits and adults, respectively. By winter 1987, Topsamelt
collected at E2 were clustered around the 25-34ma size class, suggesting new
recruits for that year. No Topsmelt were collected at El in the winter.

Size frequency analysis of California halibut (Paralichthys californicus)
collected from station E2 shows developmental patterns for that species (Figure
4). Spring collections consisted of numerous small individuals, again
indicating young of the year. Summer and fall collections were composed of
progressively fewer, larger individuals, suggesting maturation of the year 1
class. Winter collections were dominated by few small individuals, the majority
of which were from 10mm to 29mm. These represent the new year 1 age class. The
smallest California halibut collected in this study was 9mm, taken at E2 in June
1986; the largest specimen was 430mm taken at station El in November.

Gut Analysis of Juvenile Halibut

California halibut (Paralichthys californicus) are one of the few
commercially important species that inhabit southern California estuaries and
lagoons. This species spawns offshore and uses these wetlands as a nursery
ground. While the present study examines halibut distribution in Tijuana
Estuary in relation to substrate, analysis of food items for different size
juveniles was not proposed. Such an analysis was conducted on 20 juvenile
halibut that died during sampling procedures. The results (Table 4) show a
distinct pattern in food prey items taken by different size juveniles, despite
the small sample size. Halibut larger than 70mm fed primarily on gobies and
juvenile topsmelt, those between 70mm and 46mm ate mostly gammarid amphipods
with a few calanoid copepods, and those 46mm and less preyed upon the smaller
calanoid copepods with fewer gammarids. The distribution and seasonal abundance
of these prey organisms may help to clarify halibut distribution and abundance
within the estuary.

Ichthyoplankton

Six taxa of fish larvae from 5 families, and 5 taxa of fish eggs from 5
families were collected during the study period (Table 5). Larval collections
were dominated by a complex of goby species that include Arrow goby, Shadow goby
(Quietula y-cauda) and Cheekspot goby (Ilypnus gilberti). More than 99% of the
adult and juvenile gobies collected were Arrow gobies, as opposed to the other
two species, and it is assumed that the larval collections were similarly
composed. This complex comprised 86x of the total larvae collected. Longjaw
mudsucker larvae comprised 7X of the total demonstrating that spawning occurred
during the 1986 season. Whether or not this spawning event contributed
significantly to the recruitment of this species is unclear. Three additional
species contributed 7x of the total, collectively (Table 4).

Egg collections were dominated by Sciaenidae eggs, a grouping of species
that probably includes Queenfish (Seriphus politus), White croaker (Genvonemus
lineatus) and other members of the family. This taxonomic group comprised 93X

of the eggs collected. Four other species comprised the remaining 7x (Table 4).
Egg diversity was greatest at E3, the site closest to the mouth, where all five
species were collected at their highest densities.

Peak densities of goby complex larvae were collected during the November
sampling period. This coincides with a spawning peak for this taxon in 1980
(Nordby 1982) at Tijuana Estuary, although maximum spawning peaks occurred in
early spring of that year.

Sciaenidae eggs were collected In highest densities in August. This is
unusual in that this period is not considered to be a time of Sciaenidae
spawning; it usually occurs in late winter-early spring (Nordby 1982).

It was originally proposed that a comparison of flood tide and ebb tide
ichthyoplankton be made to test the model of tidal translocation as the primary
mechanism controlling ichthyoplankton distribution in Tijuana Estuary. This
model was based upon 1980-1981 findings that included nearshore spawning fish
larvae in the estuary and estuarine larvae (gobies) nearshore. However, there
have been very few specimens of nearshore larvae collected thus far in the
estuary. This may be a function of the reduced tidal prism that has resulted
from sedimentation of the main channel and sand deposition at the mouth. The
fact that the highest diversity and density of eggs were collected at the site
near the mouth suggests that a tidal mechanism is still functioning, although
this may be to a lesser degree than in 1980-1981.

Zooplankton

Macro-zooplankton populations, collected simultaneously with
ichthyoplankton in 505 micron mesh nets, were examined because of their
importance as food items for adult and juvenile fishes (M. Hellberg, unpub.
data). Although identification has been made only to family level in most
cases, gross taxonoaic composition and spatial distribution can be demonstrated
(Table 6) (dominant copepods were identified to genus level by Dr. C. Por,
Hebrew University of Jerusalem).

Fifty forms of zooplankton were identified. Collections were dominated by
brachyura zoea which occurred in densities as high as 56 per cubic meter.
Calanoid copepods comprised the most diverse group with 18 representative taxa.
One species of calanoid copepod, Arcatia sp., occurred in densities as high as
7.6 per cubic meter. Other numerically important zooplankton include decapod
zoea and gammarids (Table 6).

The greatest diversity of zooplankton was encountered at station E3, the
site closest to the mouth. This is a similar pattern to that demonstrated by
lchthyoplankton and lends support to a reduced tidal translocation mechanism.

Densities of brachyura zoea and decapod zoea were greatest at sites E1 and
E2 located furthest from the mouth, indicating that these were estuarine spawned
as opposed to tidally-transported from nearshore. Densities of calanoid
copepods were highest at stations E1 and E3.

Benthic Invertebrates

A total of 41 taxa of benthic invertebrates was collected in 1986-87, with

several reported for the first time in samples from Tijuana Estuary (Table 7).
Taxa reported for the first time include bivalve molluscs Crassostrea gigas
(Japanese oyster) and Zirfaea pilsbryi, the gastropod mollusc Tegula sp., and
decapod crustaceans Heptacarpus sp., Cancer gracilis and Calinectes sp.

Collections were dominated by the bivalves Tagelus californianus and
Protothaca staminea in the sandy substrates, and by spionid worms in the mud
substrates (Table 7). Tagelus californianus occurred in the highest densities
at station E2 followed by station E3. Protothaca staminea was also most
abundant at site E2 followed by El. In both cases, highest densities were
encountered during summer samples. Species diversity was greatest at site E2
where 26 taxa were collected , followed by E1 with 20, E3 with 13, E4 with 9 and
the one-time sampling at E5 with 2.

The occurrence of high densities of the dominant bivalves and high species
diversity at the clay/shell substrate of site E2 was unexpected. Tagelus
californianus have been collected from Tijuana Estuary in medium to fine sand
with highest densities in coarser sediments, while P. staminaea have been taken
in very coarse to fine sand with highest densities in finer sediments (Hosmer
1977). Their high relative abundances at site E2 may be due to significant
disturbances at other estuarine sites. For example, the main channel was
dredged by the U.S. Fish and Wildlife Service in 1984 to remove sediments washed
over from adjacent dunes. The mouth region near E3 has also experienced
sedimentation from recent flood events (Williams and Swanson 1987) and was
bulldozed open in late 1984. The lack of such disturbances at E2 may explain
the apparent preference of this habitat relative to other estuarine sites.

Benthic infauna in tidal creeks was low in species diversity with
relatively high densities of spionid worms. The sediments at both sites were
very fine, anaerobic mud atypical of substrates that support bivalves.
Interestingly, at both tidal creek sites, sediments at depths greater than about
15cm changed from fine mud to coarser sand with numerous shells of larger size
bivalves. This suggests that under past conditions of greater tidal prism these
areas were more productive in terms of benthic infauna.

Population densities of some benthic invertebrates were underestimated
using the coring techniques of this study. These include Callianassa
californiensis (ghost shrimp), Cerithidea californica (California horn snail)
and crab species such as Hemiqrapsus oreqonensis and Pachygraysus crassipes,
although these latter are not considered infauna. Ghost shrimp burrows were
very abundant at sites El and E3. When burrows were sampled by means of
hand-powered suction pumps, multiple individuals were found in each burrow.
Cerithidea snails were very dense in creek bottoms but this was not always
apparent in cores. Live crabs were abundant at E2 but were rarely taken in
cores. In addition, several specimens of Dendraster excentricus (sanddollar)
were taken in seines for adult and juvenile fishes. These were live individuals
that ranged in size from about lcm to 3cm in diameter and may represent the
reestablishment of a formerly abundant invertebrate at Tijuana Estuary.

In addition to the sampling conducted in this monitoring effort, R. Duggan
sampled the bivalve populations at 5 sites along the main north-south channel as
part of his thesis work with Professor D. Dexter (Figure 1). Duggan found 19
species of bivalves at these sites (Table 8). Two species, P. staminea and T.
californianus, dominated Duggan's seasonal sampling (Table 9). Densities of the
two dominant species dropped significantly from levels in September of 1986 to

those in January 1987. However, mean size increased through time in all cases.
These data demonstrate the survival and growth of bivalve recruits following
reinstatement of tidal flushing.

On December 31, 1986 and again on January 1, 1987, tides of 7.8 ft MLLW
washed dune sand into the channel at the site of station El. Although not
quantified, it is estimated that 4 to 6 inches of send were deposited in the
channel. A comparison of the benthic invertebrates at El and in an adjacent
section of the channel not affected by the wash-over illustrates the immediate
effects of such sedimentation (Table 10). The dominant bivalves at El were
eliminated while densities of other invertebrates were considerably less than in
the adjacent area. It is obvious that even short-term sedimentation events are
very harmful to the benthic infauna.

Two new areas to the south of the mouth (Figure 1) were sampled for
invertebrates in March, 1987. This channel has been receiving reduced tidal
flows due to sedimentation at the mouth, and portions of it were dredged in
1986. Station F was in an undredged part of the channel while station G was
located within a dredged reach. Thus, a comparison of the effects of dredging
on channel invertebrates can be made. The results of the southern channel
survey (Table 11) demonstrate a different bivalve community than that found in
the northern arm. The dominant species is Cryptomya californica while Tagelus
californianus and Protothaca staminea are relatively minor species. In
addition, the mean size of Tagelus californianus is large (54mm) indicating that
these specimens are several years old and thus represent successful recruitment
following mouth opening in December, 1984. Large Nacoma nasuta were also
encountered, as well as smaller individuals that lowered the mean size of this
species to 21.3mm. Cryptomya californica, on the other hand, are newly
recruited to this area as indicated by the mean size of 8.7Smm.

The comparison of dredged and undredged sites shows the short-term impact
of such activities of the channel biota. Site G contained very few bivalves and
those present represent new recruits. The rate of colonization of this area will
be followed in the second year of this program. The entire north arm of the
estuary was dredged in April, 1987 by the U.S. Fish and Wildlife Service to
remove sedimentation due to dune wash-over and improve the tidal prism. The
positive effects of dredging to improve tidal flushing must be weighed against
the short and long-term impacts to channel organisms.

Conclusions

The small tidal wetlands typical of southern California are primarily
influenced by seawater with only seasonal freshwater input. Thus, channel biota
are dominated by marine forms. Unlike estuarine organisms in areas of
continuous freshwater input, which are adapted to a range of salinities,
deviation from seawater salinities is often lethal. Recolonization from an
oceanic source may be rapid, but reestablishment of a stable community may take
several years, especially if environmental perturbations, such as drought or
flooding, continue.

At Tijuana Estuary, closure to tidal flushing and coincidental drought
resulted in the elevation of water salinities to greater than lOOppt and the
drying of intertidal habitat. Nearly all benthic invertebrates were killed,
with the exception of spionid worms. The immediate effect on channel fishes is
leas clear. Data from a graduate level SDSU Estuarine Ecology class (seven

sites, sampled once each over three dates) revealed six species - Topsmelt
(Atherinops affinis), California killifish (Fundulus parvipinnis), Longjaw
mudsucker (Gillichthys mirabilis), Arrow goby (Clevelandia los), Cheekspot goby
(Ilypnus gilberti), and Striped mullet (Mugil cephalus). If sampling was
careful and complete, the notable absence of flatfishea California halibut
(Paralichthys californicus) and Diamond turbot (Hypsopsetta guttulata), and the
benthic Pacific staghorn sculpin indicates an early, negative response of these
species to rising salinities.

Monitoring of fishes and invertebrates at Tijuana Estuary was initiated in
June, 1986, approximately 18 months following reopening of the estuary mouth.
The benthic invertebrate community was dominated by small ( (40mm) Tagelus
californianus and Protothaca staminea. The size of these bivalves indicates
that these are recent recruits, less than one year in age. Thus, 18-24 months
after the return to normal salinities, the benthic community was still unstable
and susceptible to catastrophic events.

The fish community showed a less obvious response to the stressful
conditions of mouth closure. During 1986-87 flatfish populations appeared to
recover with numerous small individuals present in the main channels. However,
populations of Longjaw mudsucker were still low, occurring in only two samples
over the entire year and in low relative abundance. Evidence suggests that this
population depression was a direct result of high salinities.

The effects of sedimentation on estuarine organisms has been well documented
(Onuf and Ouammen 1983, Darnell 1976, Sherk 1971). Sedimentation affects
filter-feeding benthic invertebrates by direct burial, habitat destruction,
impaired respiration, impaired feeding and excretory functions, retarded egg
development, and reduced growth and survival of larval stages (Sherk 1971).
Fishes are most affected by loss of invertebrate food items, interference with
respiration, and destruction of demersal eggs (Morton 1977).

The immediate and short-term effects of sedimentation examined in this study
resulted in the near total extirpation of benthic infauna in small isolated
areas. The impact on fishes was less dramatic, due to their mobile nature.
However, densities and diversity were low in areas affected by dune wash-over.
Whether this was due to mortality or avoidance of the area is not known. A
sedimentation event during spawning of a species with demersal eggs, such as the
Arrow goby and Longjaw mudaucker, could lead to depressed population levels.

Recommendations

1. Assess effects of dredging.

In April, 1987 a contractor to the U.S. Fish and Wildlife Service dredged
the main north-south channel of the estuary to remove accumulated sediments and
increase tidal prism. Additional dredging is planned for later in 1987. Due to
the large scale of this operation, many channel organisms and their habitat will
be eliminated. It is vital that the immediate effects of dredging be assessed,
i.e. the survival or mortality of infauna and associated effects on fishes.
Longterm effects such as rates of recolonization and population stabilization
can only be documented after the hydrological modifications to the system are
completed. This work will begin with the 1987-88 hOAA-OCRM-MEMD project.

2. Maintain tidal flushing while minimizing the frequency of maintenance dredge
operations.

The importance of tidal flushing to the channel organisms cannot be
overemphasized. These are marine species dependent upon tides to supply
nutrients, moderate temperatures, deliver dissolved gases and dilute waste
products.

Despite the immediate damage due to dredging, the estuarine mouth should be
maintained open if it closes. While it has been suggested that reduced tidal
circulation may be desirable for some salt marsh plants (Zedler and Covin,
1987), the overall management goals of the system must be defined. A reduced
tidal influence may favor the cordgrass-light-footed clapper rail association
over the pickleweed-Belding's Savannah sparrow association. However, the
invertebrate food supply of the clapper rail may be negatively affected by this
action while the insect-dominated foods of the Belding's Savannah sparrow might
be less so.

Efforts should be made to stabilize the hydrology of the system so that
repeated dredging is not necessary. With the current cycle of sedimentation and
dredging, the biological communities at Tijuana Estuary are in a constant state
of flux, with many species bordering on local extinction. A one-time massive
dredging oiperation, while extremely harmful in the short term, might be the
most beneficial in the long term.

3. Evaluate impacts of wastewater discharges to Tijuana Estuary.

Other hydrological issues include the management of freshwater and
wastewater inflows. Currently, renegade wastewater from Mexico flows into the
Tijuana Estuary. These inflows affect the system in two ways: the fresh water
changes a seasonal stream to one that flows year-round and potentially toxic
compounds in the wastes are discharged to the estuary. Year-round reservoir
discharge to the San Diego River marsh resulted in a shift in the vegetation
community of that system from salt marsh to brackish marsh dominated by cattail
(Typha domingensis) (Zedler and Beare, 1986). The impact of toxic compounds
such as selenium on California wetlands is currently being investigated. The
effects of wastewater addition to the Tijuana Estuary should be carefully
monitored and the discharge controlled to avoid such potential impacts.

Acknowledgements

This research was funded by NOAA Office of Ocean and Coastal Resource
Management, Marine and Estuarine Management Division Grant No. NA86AA-D-CZO 16.
I gratefully acknowledge S. Perry, J. Covin, M. Hellberg, R. Duggan, A. Setran,
X. Drawbridge and T. Griswold for field assistance; R. Duggan and X. Hellberg
for the use of their data; K. Dyke for laboratory analysis of fishes and
invertebrates; and, J. DeWald for report production assistance.

Literature Cited

Allen, L.G. 1980. Structure and productivity of the littoral fish assemblage
of Upper Newport Bay, California. Dissertation. University of Southern
California, Los Angeles, California.
Brothers, E.G. 1975. The comparative ecology and behavior of three sympatric
California gobies. Dissertation. University of California San Diego. San
Diego, California.
Darnell, R.M. 1976. Impacts of construction activities in wetlands of the
United States. United States Environmental Protection Agency.
EPA-600/3-76-045
Hosmer, S.C. 1977. Pelecypod-aedinent relationships at Tijuana Estuary.
Thesis. San Diego State University. San Diego, California.
MacDonald, C.K. 1975. Notes on the family Gobiidae from Anaheim Bay. IN Lane,
E.D.; Hill, C.W., (Editors). The Marine Resources of Anaheim Bay.
California Fish and Game Fish Bull. 165.
McIllwee, W.R. 1970. San Diego County coastal wetlands inventory: Tijuana
Slough. Unpublished report to the Calif. Dept. Fish & Game, Game Habitat
Development.
Morton, J,W. 1977. Ecological effects of dredging and dredge spoil disposal:
A literature review. Tech. Paper 94 of the U.S. Fish and Wildl. Serv.
U.S. Dept. of Int. Fish and Wildl. Serv. Wash, D.C.
Nordby, C.S. 1982. The comparative ecology of ichthyoplankton within Tijuana
Estuary and in adjacent nearshore waters. Thesis. San Diego State
University. San Diego, California.
Onuf, C.P. and M.L. Quammen. 1983. Fishes in a California coastal lagoon:
effects of major storms on distribution and abundance. Mar. Ecol. Prog.
Ser. 12: 1-14.
Rudnicki, R.M. 1986. Dynamics of macroalgae in Tijuana Estuary: response to
simulated wastewater addition. Thesis. San Diego State University. San
Diego, California.
Sherk, J.A. 1971. The effects of suspended and deposited sediments on
estuarine organisms: literature summary and research needs. Chesapeake
Biol. Lab. Solomons, Md. Contrib. No. 443, 73 pp.
Tasto, R.N. 1975. Aspects of the biology of the Pacific staghorn sculpin,
Leptocottus armatus, in Anaheim Bay. IN Lane, E.D.;Hill, C.W. (Editors).
The Marine Resources of Anaheim Bay. California Fish and Game Fish Bull.
165.
Williams, P.B. and M.L. Swanson. 1987. Tijuana Estuary Enhancement Hydrologic
Analysis. San Diego State University Foundation.
Zedler, J.B. and P. A. Beare. 1986. Temporal variability of salt marsh
vegetation: the role of low salinity gaps and environmental stress. IN D.
Wolfe (Editor). Estuarine Variability. Academic Press.
Zedler, J.B. and J.D. Covin. 1987. Salt marsh monitoring and plant
reestablishment at Tijuana Estuary. NOAA Technical Memorandum.

PACIFIC
OCEAN

I r
I KM

Figure 1. Sampling stations at Tijuana Estuary, CA. Sites A-G from R.Duggan
in Progress.

Species Diversity by Season

'I -~~~~~~~~

I
20
#A

Sampling Date

Figure 2. Species diversity of adult and juvenile
fishes collected on 4 dates at Tijuana
E-stuary, CA. in 1986-87.

Species Diversity by Sampling Site
1*
a~~~~~~~~~~~~~~~~~~~~

EE
Sampling Site

Figure 3. Species diversity of adult and juvenile
fishes collected from 5 sites at Tijuana
Estuary, CA. in 1986-87.

Station 2 3/10/87 Catch Per Unit Effort
300 .~
y = 160.3081 - 0.0992x R = 0.39

l
200 4

{at~~~ ~ , t -~ Total fish
100 1 '

oo
O I , , ,
0 200 400 600 800
Prior Cumulative Catch

Figure 4a, Catch per unit effort of adult and juvenile
fishes at station E2 on 3/10/87.

Statlon 2 3/11/87 Catch Per Unit Effort

160
y = 15B.6573 - 0.1066x R= 0.93

140-

120- ~ Fish caught

too

80 . . . . . . . . . .
0 100 200 300 400 500 600
Prior Cumulative Catch

Figure 4b. Catch per unit effort of adult and juvenile
fishes at station E2 on 3/11/87.

Station 2 3/10/87
300

200 -
jB 2O0smeltc- 200 Lotal fish
\-c\ - *- ~Topsmelt
- Arrow 6oby
,A ! .1 -/- Sculpin
100 \\-//i Flatfish

0
0 1 2 3 4 5 6 7
Seine '

Figure 5a. Species composition of repeated seinings at
station E2 on 3/10/87.

Station 2 3/11/87
200-

- Total tish
Topsmelt
100- U Arrow Goby
c-- Sculpln
Killifish
1D- Flatfish

0 1 2 3 4 5 6
Seine �
Figure 5b. Species composition of repeated seinings at
station E2 on 3/11/87.

Station 1 5121 /86

300 -

.t 200-

0 ioo 200
Size cuss in mm

Station 1 8118/96

60 -

4" 4~-l40 -G Topsmelt

20 -
100-0 0
E

0 -
0 100 200

Size class in mm

Station 1 11825/86

80-

20-

4-- Topsmelt
'I'O

0 100 200
Size class in mm
Figure 6. Size frequency analysis of Topsmelt at station El.

Station 2 5/22/86

200 -

100 -
_ 100 a- Topsmelt

Size class in mm

Station 2 8113186

60-

50 -

40-

~~~~~ " ~~~~~~~~~Topsmelt

20 -

10.

0 100 200
Size cuss in mm

Figure 7. Size frequency analysis of Topsmelt at station E2.

Station 2 11/24 86

60 -

50 -

40-

30- Topsmelt

20-

E 10 -
0 l-

0 100 200
Size class in mm

Station 2 3/10/67

80 -

60 -

I 40-
-- Topsmelt

0
0 100 200
Size class in mm

Figure 7. Continued.

Station 2 5/22/86

12 -

10-

6-
� 8 -B- Ca1 halibut

0
0 100 200
Size class in mm

Station 2 8113/86

a 3-

2-
�C 2 - l lo-- Cal halibut

A 1-

0 100 200
Size class m mm

Figure 8. Size frequency analysis of California halibut at
station E2.

Statiso 2 11124 86

12-

1.0- FX1 f l

0.8-

0.6- -e- Cal halibut

0.4-

0.2-

0.00
0 100 2[00
Size class in nmm

Station 2 3/10/57

Cal halibut

13 '9I~ �"�

Size cassr in mm

Figure 8. Continued

Table 1. Taxonomlic composition, relat we abundance and densities of adult and juvenile fishes collected at 5 sampling sites at Tijusna
Estuary, CA. Densities (flim ) are shown in parentheses.

Number collected and density per sampling site per date
Density (to ) In parenthesis
El 12
Taxon Comn" Name Spring Sumer Fell Winter spring Sumser Fail Winter
Atherinidas
Atherinops affinis Topsumlt 3629(23.0) 401(9.5) 55(0.8) 4340(14.5) 231(3.5) 584(6.5) 172(1.8)
Ulenniidse
HyftLob.1enniUP gilberti lockpool slenny 1(<O.I)
f,,.ob ...annu jenksin Mussel Blenny t(<0.I) 1<.I
flothidase
Paralichthys californicus California 33(0.2) 3(<0.t) 3(<O.t) t(<0.1) 43(0.1) 14(0.2) 6(<O.l) 18(0.2)
Ralibut
Cottidee
Leptocottu!. aruatus Pacific 186(.2) 4(<0.1) 2(<0.l) 15(0.2) 16(<0.1) 64(0.67)
Staghorn Sculpin
Artedins Sp. Sculpin 2(<O.1)
cyprin-odontidas
rundulus paripfunnl California 58(1.4) 77(1.1) 6(<0.1) 155(2.3) 12(0.1)
Killifish
gagrealididast
AMchoe ages Deep Body Anchovy W(0.1) 2(<0.1)

Girella sircn Opaleys 9(0.2) 70(m.)

Clovelandia ION Arrow Coby 174(1.1) S(0.1) 2(<0.I) 4(<0.1) 5(<0.l) 6(0.l) 608(6.4)
xll;;Zu WGilbrif Cheekopot Toby l(<0.) 7(0.2) 1(<0. 1)
Quieto Y-caudd Shadow Goby
Gllfhty--aI~I~Ibii Longiaw Mudsucker 39(0.6)

NPItIMLKIVIU Striped Mallet 3(<0.t)

Hypeopuetta Ruttulata Diamond Turbot 1(<0.t) 1((0.1) 2(<0.1) 4(<0.1) 10(0.1)
Pleuronichthys ritteri Spotted Turbot 3(<O.1) 1(<0. 1)
thinobatidae
thinobaton productus Shovelnose t(<0.1)
Sultarfish
Serraidaee
Parslabrax clathratus Kelp sassme0.1
Sc isenidae
Sethepolitus Queenfish t(<0.I)

Syngnathus leptorhynchus Say Ptpeflsh S(<0.1) 1(<0.1) 1 (<0.1)

Station 5 - Sampled In lieu of Station 4 during fall sampling period

Table 1. Continued.

93 14 15
Spring Saner Fall Winter spring Suaner Fall

1062(7.1) 349(14.2) 1(<0.1) 313(1094.3)

23(0.15) 349(14.2) 110(4.5) 1(<.01) 3(1.0) 176(9.5)

1(C0. 1)

1043(7.0) 6178(252) 204(8.3) 302(12.0) 360(120) 10(0.5) 23(5.8)
25(0.2) 12(0.5) 2(C0.1)
3(CO. 1)
2(0.7)

7(<0. 1) 9(0.4)

Table 2. Physical characteristics of 5 sampling sites at Tijuana Estuary, CA.

X X
Sampling Dissolved Temperature Salinity Time Channel Channel
period 02(ppm) (ppt) morphometry substrate
(width x depth)

6/86
Station El 6.2 20.5 35 1045 13m x .75m sand
sloping to steep sides
Station E2 6.5 27 38 1200 12m x Im clay/shells
steep sides
Station E3 4 22 38 1130 10m x .5m sand/mud
sloped sides
Station E4 saturated 27 37 1200 2m x O.lm mud
sloped sides

8/86
Station El 6 23 34 1440 14m x .5m
Station E2 2 25 34 1000 12m x .3m
Station E3 saturated 29 34 1100 10m x .3m
Station E4 N.D. N.D. N.D. 1300 2m X .5m

11/86
Station El saturated 16.0 33 1110 13m x .5m
Station E2 8.1 16.5 ,4 1330 12m x .75m
Station E3 8.15 15 34 1015 10m x .3m
Station E5 8.0 16.5 33 1200 2m x .lm

3/87
Station El 7.6 15.0 32 1045 13m x .5m
Station E2 7.0 12.5 34 1340 13m x .45m
Station E3 saturated 20.5 34 1400 lOm x .3m

Table 3a. Comparison of adult and juvenile fishes and ichthyoplankton
collected from Station El on consecutive days. Numbers in
parentheses = mean density.

Number collected
11/25 11/26

ADULTS AND JUVENILES

Atherinops affinis Topsmelt 55 56
Clevelandia ios Arrow Goby 2 0
Paralichthys californicus California Halibut 3 2
Leptocottus armatus Pacific Staghorn Sculpin 2 1
Fundulus parvipinnis California Killifish 77 29
Hypsopsetta guttulata Diamond Turbot 0 2

LARVAE

Atherinops affinis Topsmelt 0 7(0.02)
Artedius sp. Sculpin 9(0.02) 0
Goby complex Gobies 300(0.6) 246(0.6)
Gillichthys mirabilis Longjaw Mudsucker 6(0.01) 4(0.0,)

EGGS

Citharichthys spp. Sanddab 4(0.04) 2(0.008)
Sciaenidae Croakers 4(0.01) 2(0.008)

Table 3b. Comparison of adult and juvenile fishes collected from Station E2 on
consecutive days.

Number collected
3110 3111

ADULTS AND JUVENILES

Atherinops affinis Topsmelt 172 157
Clevelandia ios Arrow Goby 608 502
Paralichthys californicus California Halibut 17 *
Leptocottus armatus Pacific Staghorn Sculpin 64 68
Fundulus parvipinnis California Killifish - 11
Hypsopsetta guttulata Diamond Turbot 10 *
Hypsoblennius jenkinsi Mussel Blenny 1 -
Ilypnus gilberti Cheekspot Goby 1 -
Syngnathus leptorhynchus Bay Pipefish 1 -
Flatfish combined 13

Table 4. Halibut gut analysis.

Size of Specimen Gut Contents

1) 17 mm 10 calanoid copepods
2) 17 mm 6 gammarids amphipods, 5 calanoid copepods
3) 18 mm 4 gammarid amphipods, 50 calanoid copepods
4) 24 mm 20 calanoid copepods + fragments
5) 34 mm 6 gammarid amphipods, 75 calanoid copepods
6) 43 mm 5 gammarids amphipods, 52 calanoid copepods
7) 46 mm 20 gammarid amphipods, 7 calanoid copepods +
fragments
8) 46 mm 200+ calanoid copepods
9) 49 mm 4 gammarid amphipods + fragments
10) 60 mm 34 gammarid amphipods + fragments
11) 61 mm 34 gammarid amphipods + fragments
12) 61 mm 14 gammarid amphipods
13) 63 mm 21 gammarid amphipods + fragments
14) 72 mm 2 Arrow Goby 30 mm, 17 mm
15) 73 mm 2 unidentified fish, 5 gammarid amphipods
16) 104 mm 1 Arrow Goby, 26 mm
17) 105 mm 1 Arrow Goby, 38 mm
18) 111 mm 3 Arrow Goby, 15 mm, 13 mm, 18 mm
19) 113 mm 3 Arrow Goby, 15 mm, 13 mm, 15 mm,
5 Topsmelt, 19 mm, 22 mm, 20 mm, 12 mm,
23 mm
20) 149 mm All contents partially digested -
non-identifiable

Table S. Taxonomic composition, number collected and mean density (Ito 3 per sample of fish eggs and larvae collected at 3 sampling sites at Tijuana.
Estuary, CA. Density figures in parenthesis.

1ARVAS at E2 33
Taxon spring Burnr Pall poll Winter Summer F all Winter Summer Fall Winter
(11125) (11126)

Atherinidas
Athortoopa affinvis 1(0.001) 7(0.02) 7(0.02)

Cottidee
Artedium op. 2(0.005) 9(0.02) 25(0.08) 2(0.005) 2(0.07)

Cobiidaa
Coby complex 2(0.005) 300(0.6) 246(0.6) 198(0.3) 3(0.008) 4(0.03) 4(0.01) 11(0.03)
Gillichthys mirsbilis 6(0.01) 40(0.1) 15(0.02) 6(0.02)

Pleurosectidas
Pleuronichithys ritteri 1(0.01)

tograwlidae
UNOSAVlis mordex 4(0.005)

EmGs

Bothidae
Cithavichthys app. 10(0.02) 4(0.04) 2(0.008) 6(0.08) 4(0.01) 5(0.01) 2(0.07) 2(0.005)

Ophidlidge
Odophidium scrippai 26(0.06)
Pleuronectidas
Fleuronichthys ritteri I(0.002)

Sciasnidee spp. 7(0.02) 4(0.01) 8(0.01) 2(0.008) 5(0.01) 665(1.5) 1(0.002)

Scombidas
Scouber japonicus 1(0.002)

Table 6. Mean densities (n=3) of zooplankton collected from 3 sampling stations at
Tijuana Estuary July 22 through August 4, 1986. Data from M. Rellberg,
unpublished.

El E2 E3
Flood Ebb Flood Ebb FFlood Ebb
Tide Tide Tide Tide Tide Tide

Brachyura zoea
A 10 56.1 6.0 12.8 0.0 1.7
B 1.8 9.3 1.3 4.1 0.02 0.3
C 0.01 0.01

Brachyura megalops
A 0.01
B 0.01

Decapod zoea
A 0.4 0.62 1.22 1.2 0.03 0.02
B 0.01 0.04 0.02 2.0 0.23
C 0.01 0.01

Decapod megalops
A 0.005 0.01

Calanoid copepod
A Arcatia sp. 7.6 7.1 0.63 1.1 3.6 0.31
B Labidocera sp. 0.005
C Pseudodiaptomus sp. 0.01 0.02 0.01 0.005 0.01
D Centropages sp. 0.01 0.02 0.06 0.01
E Pseudodiaptomus sp. 0.02 0.004
F Labidocera sp. 0.01 0.02 0.21 0.74 0.01
G Pseudodiaptomus sp. 0.02 0.01 0.02 0.14 0.01
H Centropages sp. 0.01 0.02 0.03 0.01
I
J 0.06 0.01
K 0.02 0.004
L 0.004
M 0.02
N 0.02
0 0.01
P 0.01
Q 0.005
R 0.005

Chaetognath 0.05 0.04 0.24 0.15 0.01

Gammarid
A 0.18 0.05 0.01 0.02 0.005 0.004
B 0.14 0.04 0.24 0.64 0.09 0.10
C 0.05 0.004
D 0.01 0.01 0.01

Hydrozoa medusae
A 0.01
B 0.005
C 0.01
D 0.06 0.01

Table 6. (Cont.)

El E2 E3
Flood Ebb Flood Ebb U0Flood Ebb
Tide Tide Tide Tide Tide Tide

Isopod
A 0.01 0.01
B 0.004
C 0.005

Balanus nauplius 0.01

Bivalve 0.02 0.02 0.01

Cyclopoid copepod
A 0.01 0.01
B 0.01 0.01
C 0.01 0.01 0.03 0.01

Harpacticoid copepod
tisbe sp. 0.01 0.01

Hypertid

Pychogonid 0.005

Worm-like forms
A 0.01
B 0.01
C 0.01
D 0.01
E 0.01
F 0.01

Mysid larvae 0.02 0.01 0.02 0.16 0.06 0.02

Unknown 0.04 0.004

Copepod nauplius 0.01 0.004

Tal 1 enthic invertebrate* collected at 5 sampling sites at Tijuana Estuary, Ch. Quar~erly sampling periods are designtetd an Sp - Spring;
S - gumner; 7 - Fall; W - winter. Numbers to parentheses are mean densities (0lu ) to a 20 en depth. + - Present in samples.

Taxon E l X2 E3 9
Sp S 7 W S p S P V BP S 7 W Sp S 7

SIPUMCULIO WORMS 2(60) 18

IRCHINOID ECRIMODER1S
Dendraseter excentricue 3(91) 2(48)

POLYCHARTH WEORMS
Clyceridae + 1(30) 1(20)
Wereidme 1(30) 5(121)
Spionidae 1(8) + 13(525) 10(404) 12(485)
Polynoidae 1(20)
Unknown i. 1(30) + 3(121)
Rephtyidae 1(19)
Capttellidmee18 +

SIVALYR MOLLUSCS
Togolus californianus 16(485) 32(146) I($) 126(3318) 18(595) 71(401) + 95(2303) 8(150)
Maccm& naeuta 6(181) 3(91) 4(23)
Ostrea lurid& 1(30) 1(6i)
Bolan rosace-um
Crassostreams 1(30)
Mytilus edulia + 2(60O) +
Protothaca nFsuinea 23(697) 4(01) + 30(909) 15(455) 28(158) + 8(264) 1(19)
Protothaca sP. 1(30)
Zirree seab r 1(30) + +
Lesv~ardim suetritum 3(91) + 13(73) +
chlos caifornefteis 1(30) +
Mactridee + 1(fi)
Saxidoma. nuttalli 1(6)

GASTROPOD MOLL.USCS
CerithIda. californica + 5(101) 1(8) 8(212) 2(48) 412 (9 (0) Ml
lassearus tea + 5(101) + 6(182)
Acteoclas ra-cal-t 1(24)
flaminosa virescens 4(97)
CTeidl fornicate 1(30)
P.130 2(81)
"ama~ olivacaus2(1

Table 7. (Cont.)

Tasolk El2 193
Sp S F v B Sp S w Sp B P F

DECAPOD CRUSTACRAIS
Herptacarpus sp. 3(61) 6(182) 4(121)
Rmlairapauu orep~onaenld 1(30) 1(20) 4(121) 3(121)
Portanae mautuai 2(61)
carltansmA 4- 3(91) 1(20) 1(s) + 1(24)

Cacerlo," "racilIt 2(61) +

Pachgrauuucramelpes +
Uca creaulata +

150POD CRUSTACEAS
locloole op. 1(30)

ISACKTOPODA
clottidia albdas 1(30)

Table 8. Bivalves collected from 5 main channel sampling sites at Tijuana
Estuary, CA. Data from Duggan, in prog.

Tagelus sp.
Protothaca staminea
Laevicardium substriatum
Solen rosaceus
Macoma nastuta
Zirfea pilsbryi
Cryptompa californica
Saxidomas nuttalli
Sanguinolaria nuttalli
Chione undatella
Chione californica
Mactra californica
Florimetis obesa
Copperella subdiaphinia
Lyonsia californica
Petricolas sp.
Platydon cancellatus
Tellina modesta
Tellina carpenteri

Table 9. Densities of dominant bivalves collected from 22a"in channel site. at Tijuana Istuary during September 1986 and January 1987 (Data from
Duggan, in progress). Density expressed as #/a to a 20 en depth.

Site A Site U Site C
Sept. '86 Jan. '87 Sept. '86 Jan. '87 Sept. '86 Jan. '87
Taxon I density I size I density X size I density X size f density X site I density I size P density X size

Protothaca
statinea 109 2,642 9.39 90 1,019 10.8 43 1,042 10.03 77 871.5 10.7 136 5,495 7.97 69 780 10.6

TaTe ISO180 4,363 31.82 167 1,890 38.4 91 2,206 35.63 32 362.2 37.8 44 1,778 25.89 30 339 33.6
a =ffornisaus

Lesvicardium 18 436 12.72 8 194 14.9 it 8 323 13.23 5
substriatum

Cryptomys 1 24 4 97 15.46 3 121 4.57 1
californica

Solon 6 145 28.15 2 1 24
rosaeous

Macoms 3 73 23.9 3 3 73 1 2 81 16.2
nasuta

Chione 1 24 2
unfa-ella

Zirfaes sp. 3 73 30.43 3

Sa lolaria 1 24

usMculus 1 40
senhousei

Saxidomas 3 1

Florimeti I

Copperella 2

Lyonsra 1

Petricola 2

sxt. of Table 9

Site D Site E
Sept. '86 Jan. '87 Sept. '86 Jan. '87
t density X size I density X size I density X size I density X size

19 461 9.87 11 124.5 11.2 5 121 7.04 0

42 1,018 34.87 8 90.5 42.8 86 2.085 34.02 45 509.3 39.7

1 24

1 24 1 24

1 2 80 54.05 23

I I

Table 10. Benthic invertebrates collected from areas impacted by sedimentation
from dune wash-over (El) and adjacent sites not impacted (Ela) in
March 1987.

Site
Species E1 i (X density) Ela i (X density)
n-7 n 4

BIVAVE MOLLUSCS

Tagelus californicus O 14 (198)
Protothaca staminea 0 2 (28)
Macoma nasuta 0 2 (28)

GASTROPOD MOLLUSCS

Cerithidea californica 1 (8) 0

SIPUNCULID WORMS 1 (8) 7 (99)

POLYCHAETE WORMS
Nephtyidae 0 2 (28)
Capitellidae 1 (8) 9 (127)
Spionidae 1 (8) 7 (99)

DECAPOD CRUSTACEANS
Callianassa californiensis 1 (8) 3 (42)

Table 11. Mean densities (n-5) of bivalves collected at a dredged (Site G) and
non-dredged (site F) area of southern channel at Tijuana Estuary, CA.

Site F Site G
# X density X site f X density X site

Tagelus californicas 11 124.5 54 1 18.9 -
Cryptoma californica 112 1267.7 8.75 3 56.6 8.33
Protothaca staminea 3 33.9
Macoma nasuta 15 169.7 21.3
Laevicardium substriatum 5 56.7 7.4
Tellina carpenteri 1 11.3
Musculista senhousii 1 11.3

rJP-RT OCbUMENTAT1bON L RtOT NO. .L 2c.er Nte =u, Co.

Mav. 31. 1987
Monitoring of Fishes and Invertebrates at Tijuana Estuary.;
.luftholr) 8. NIL W sI Orlfngtion Reot. No.

* PHerfor~in Organ~izsta~or Nbm. ao Adres v10. Pt/TasakWoo Unit No.
San Diego State University r
San Diego, CA 92182 11. =~~-.m Gr CnttG) A.

ie1
., SIpooneifl OI(atiom Name an Addfess L TypI of R.on & hertnod Cover.n

NOAA
Office of Ocean and Coastal Resource Management =~
Marine and Estuarine Management Division
I Supoemunty Notee

Fishes and invertebrates responded differently to the impacts of elevated :

Ai at (Unmt MM ,M,

Fishes and invertebrates responded differently to the impacts of elevated
water salinities and temperatures due to the closure of the estuary mouth;
sedimentation as the result of dune sand deposition in estuarine channels;
and, dredging to remove those sediments. Increased salinities'resulted in
the mortality of all benthic invertebrates except spionid worms. Four
species of fish showed a negative response to salinities greater than 50 ppt.
Gillichthys mirabilis, the longjaw mudsucker, populations showed a lag response
*o salinity with numbers declining in 1986-87. Sedimentation events resulted
in the elimination of bivalve species and decreased densities of polychaetes.
Dredging to remove sediments resulted in the coincidental removal of all types
of benthic invertebrates. ,ecruitment from an oceanic source is rapid, with small
individuals suseptible to further environmental fluctuations.

Estuaries, fishes, benthic invertebrates, sedimentation, salinity, dredging.

s" �o"
dlmerlfismt0mg Rw ?

a" sirr-as
--~ ~ 0-f i ii2

NOAA TECHNICAL MEMORANDUM

NOS MEMD

TIJUANA RIVER NATIONAL ESTUARINE RESEARCH RESERVE

Christopher S. Nordby

31 May 1987

U.S. DEPARTMENT OF COMMERCE
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
OFFICE OF OCEAN AND COASTAL RESOURCE MANAGEMENT
MARINE AND ESTUARINE MANAGEMENT DIVISION
WASHINGTON. D.C.

This report was prepared as an account of government-sponsored work and
has been approved for distribution. Approval does not signify that the
contents necessarily reflect the views and policies of the government, nor
does mention of trade names or commercial products constitute endorsement
or recommendation for use.