Post on 11-Jan-2023
ORIGINAL PAPER
Fish community responses to ecosystem stressors in coastalestuarine wetlands: a functional basis for wetlandsmanagement and restoration
Sharook P. Madon
Received: 14 December 2006 / Accepted: 18 November 2007 / Published online: 6 December 2007
� Springer Science+Business Media B.V. 2007
Abstract Functional responses of estuarine fish
species to environmental perturbations such as wet-
land impoundment, changes in water quality, and
sediment accretion are investigated. The study
focuses on the feeding, growth and habitat use by
California killifish (Fundulus parvipinnis), topsmelt
(Antherinops affinis), and juvenile California halibut
(Paralichthys californicus) in impacted coastal wet-
lands to provide an ecological basis for guidance on
the management and restoration of these ecosystems.
The ecology of California killifish, Fundulus parvi-
pinnis, is closely tied with the marsh surface, which
they access at high tide to feed and grow. Field
estimates of food consumption show that killifish can
increase their food intake by two-fold to five-fold by
adding marsh surface foods to their diet. Bioenerget-
ics modeling predicts that killifish can grow over an
order of magnitude faster if they add intertidal marsh
surfaces to their subtidal feeding areas. Tidal inlet
closures and increased marsh surface elevations due
to sediment accretion can restrict killifish access to
the marsh surface, affecting its growth and fitness. An
open tidal inlet and tidal creek networks that allow
killifish to access the marsh at high tide must be
incorporated into the restoration design. Topsmelt
and California halibut are also adversely affected by
tidal inlet closures. Food consumption rates of
topsmelt are 50% lower when the tidal inlet is closed,
compared to when the estuary is tidally-flushed. Tidal
inlet closures inadvertently induce variations in water
temperature and salinity and negatively affect growth
of juvenile California halibut. Tidal creek networks
which consist of channels and creeks of various
orders are also important to halibut. Large halibut
([200 mm TL) inhabit deeper, high order channels
for thermal refuge, while small halibut (\120 mm
TL) are abundant in lower order channels where they
can feed on small-sized prey which are typically less
abundant in high order channels. Maintaining an open
tidal inlet, implementing sediment management pro-
grams and designing coastal wetlands with tidal creek
networks adjacent to intertidal salt marsh habitat (for
fish access) are key elements that need to be
considered during the planning and implementation
of coastal wetland restoration projects.
Keywords Salt marshes � Lagoons �Indicators of anthropogenic stressors �Estuaries � Fish ecology
Introduction
Coastal wetlands in southern California have expe-
rienced substantial anthropogenic alterations in the
S. P. Madon (&)
Water Resources and Environmental Management
Practice, Ecosystem Planning and Restoration, CH2M
HILL, Inc, 402 W. Broadway, Suite 1450, San Diego,
CA 92101, USA
e-mail: smadon@ch2m.com
123
Wetlands Ecol Manage (2008) 16:219–236
DOI 10.1007/s11273-007-9070-6
past century. Increased human populations along the
coast have led to an accelerated loss of wetland
habitat and resulted in the fragmentation of remnant
coastal wetland habitats (Zedler 2001). Most wet-
lands along the southern California coast are bisected
by railroad tracks and roadways, and compromised
by the development of housing complexes, marinas,
docks, tide gates, culverts and dikes (Zedler 1996a,
2001). As a result, the tidal prism in these wetlands is
greatly reduced, often causing the ocean inlets to
close, with resultant changes in water quality and
water level (PERL 1990; Zedler et al. 1992, Zedler
1996a, 2001) that can negatively affect wetland biota
(Nordby and Zedler 1991). Most of the region’s
coastal wetlands have closed to tidal flushing peri-
odically, and sometimes for several months (Zedler
2001). Episodic sedimentation is also a problem in
these wetlands (Zedler et al. 1992, Zedler 2001), with
sediment accretion rates in excess of 1 cm yr-1 at
certain sites (Onuf 1987; Callaway and Zedler 2004;
Thrush et al. 2004; Wallace et al. 2005). High
sedimentation rates can have profound effects on
estuarine biota. Episodic deposition of sediments, on
one hand, can directly cause mortality of benthic
organisms via smothering. More subtle effects of
sediment accretion include increases in marsh surface
elevations and subsequent changes in marsh inunda-
tion patterns that affect use of the marsh surface by
fish during high tides (West and Zedler 2000; Madon
et al. 2001).
Wetland mitigation, restoration and creation prac-
tices are increasingly being used to compensate for
anthropogenic impacts to coastal ecosystems and for
the loss of wetland habitats (Zedler 1996b). Often, a
major goal of such projects is to provide habitat and
support a variety of ecological functions for fish
populations including feeding, nursery support and
refuge from predators (Zedler et al. 1997; Williams
and Zedler 1999). Coastal wetlands in southern
California support unique fish assemblages valued
for their contribution to the region’s biodiversity and
food web support (Onuf et al. 1979; Swift et al. 1993;
Horn and Allen 1985; Kwak and Zedler 1997; Horn
et al. 1999). Studies have shown that among other
factors, the composition of these fish assemblages is
related to channel habitat characteristics and channel
morphometry (Williams and Zedler 1999; Desmond
et al. 2000). Thus, restoration projects that are
planned and implemented to more closely
approximate the hydrogeomorphic characteristics of
a natural marsh would likely provide greater func-
tional support to fish communities than those that
lack these important habitat features.
Assessment of restoration projects that utilize
better estimates of fish habitat function based on
feeding, growth and individual and community-based
species trends, rather than commonly used measures
such as species diversity and abundance has also been
recommended (Williams and Zedler 1999). Scientists
and restoration practitioners generally agree that
mitigation and restoration should be modeled on
natural systems and functional processes (Brinson
and Rheinhardt 1996). However, some restoration
projects in southern California have simply involved
the excavation of deep sub-tidal basins or channels
for fish habitat, rather than intertidal creek networks
seen in natural systems (Zedler 2001). Due to the lack
of intertidal creek networks, these designs have little
marsh-creek connectivity and a highly reduced
marsh–water interface, and may curtail use of the
marsh surface by fish during high tides (West and
Zedler 2000; Madon et al. 2001).
The need for a set of guiding principles for coastal
wetland restoration and management practices is
acute, especially in the heavily urbanized southern
California region. For restoration to be a success, it is
critical that ecologically meaningful elements are
incorporated into the restoration design and that
management practices are based on supporting eco-
logical function.
This study shows how investigations of functional
responses of estuarine fish species to specific envi-
ronmental perturbations can be effectively used to
guide the restoration and management of coastal
wetlands. The three species, California killifish,
topsmelt and California halibut, represent various
trophic levels in the estuarine food web and together
provide a broad representation of the diversity of
ecological function in the fish community. For
example, the California killifish, Fundulus parvipin-
nis, is a year-round salt marsh resident, and can be
classified as a secondary consumer, primarily feeding
on macroinvertebrates in subtidal channels and the
marsh surface. The topsmelt, Antherinops affinis, is a
pelagic schooling species common in estuaries and
nearshore coastal waters in southern California.
Juvenile topsmelt are primarily secondary consumers
and feed on macroinvertebrates, switching to a diet
220 Wetlands Ecol Manage (2008) 16:219–236
123
consisting of macroalgae (primary consumers) as
adults. The California halibut, Paralichthys califor-
nicus, is a coastal marine species that primarily uses
estuaries and lagoons as nursery areas for refuge from
predation and to support feeding and growth of
juveniles. Newly settled juvenile halibut (\50 mm
total length, TL) are primarily secondary consumers
that feed on macroinvertebrates, but switch to a
piscivorous diet (tertiary consumers) at larger sizes.
Juvenile halibut spend from 1 to 2 years in estuaries
and lagoons, moving back into coastal marine
environments once they reach a size of approximately
200–250 mm TL.
The objectives of this study are, (1) to evaluate
feeding, growth and habitat use by California killi-
fish, topsmelt and California halibut in coastal
wetlands impacted by tidal inlet closures, excessive
sedimentation, sharp variations in water quality, and
disruption of tidal inundation patterns, and (2) to use
what is learnt from these assessments as an ecological
basis for guidance on the restoration and management
of these wetlands.
Materials and methods
Study sites
Fish were sampled at two estuarine locations in San
Diego County, California: the Tijuana River
National Estuarine Research Reserve (henceforth
called Tijuana Estuary) and Los Penasquitos
Lagoon (Fig. 1). Tijuana Estuary is located just
north of the U.S.-Mexico border (32�340 N,
117�70 W) and at 1024 ha is one of the largest
remaining estuarine salt marshes in southern Cali-
fornia. Unlike other estuarine systems in southern
California, where salt marshes areas are criss-
crossed by railroad lines and roadways that affect
the tidal prism and cause frequent closures of the
tidal inlet, Tijuana Estuary’s salt marsh habitat is
one of the least fragmented and has remained
almost continuously open to tidal circulation
(Zedler 2001). Approximately three-fourths of
Tijuana Estuary’s watershed, however, lies in
Mexico, where increasing human populations,
unstable slopes and soils, inadequate sewer systems
and agricultural runoff contribute to water quality
problems and high sediment loads in Tijuana
Estuary (Zedler 2001). Episodic flood events in
the past two decades have deposited high loads of
sediment into the channels and salt marsh areas,
resulting in unnaturally high salt marsh elevations
at certain locations within the estuary and reduced
tidal inundation of the marsh surface (Ward et al.
2003; Zedler 2001).
Los Penasquitos Lagoon (32�560 N, 117�150 W) is
a relatively small salt-marsh (252 ha) with tidal
channels that typifies many fragmented coastal
wetland habitats in southern California. The lagoon
is bisected near the tidal inlet by a roadway, through
its center by a railroad, and through its southeastern
portion by a berm over a sewer line (Zedler 2001).
As a result, tidal flushing in the lagoon is impeded
and the inlet frequently closes to tidal circulation
(Zedler 2001). Extensive development in the
255 km2 watershed in recent decades has increased
freshwater and sediment input to the lagoon (Zedler
2001).
Fish sampling
California killifish, topsmelt and California halibut
were sampled at various sites between October 1998
and November 1999 in Los Penasquitos Lagoon and
Tijuana Estuary (Table 1, Fig. 1) for the purpose of
estimating their food consumption and diet compo-
sition. California halibut were also collected in
routine quarterly surveys (March, June, September,
December) as part of a long-term monitoring program
to evaluate fish community patterns at three estab-
lished monitoring sites in Tijuana Estuary (Table 1,
Fig. 1). In Tijuana Estuary, the ‘‘Mouth’’ site (M) is
located in a shallow side channel (mean depth at low
tide 0.26 + 0.03 m) approximately 0.35 km from the
ocean entrance of Tijuana Estuary and consists of a
substrate composed of organic sediment. The ‘‘Sea-
coast’’ site (SC) is located 1.34 km from the ocean
entrance in a broad, deep channel ([20 m width and
mean depth at low tide of 0.71 + 0.04 m) composed
mainly of sandy sediments. The ‘‘East-West’’ site
(EW) is in a connector channel located about 1.87 km
from the ocean entrance between the northern arm of
the estuary the inland ponds (Fig. 1). The EW site is
11 m wide with a mean depth of 0.56 + 0.04 m at
low tide, and has a clay substrate lined with cobble
and empty bivalve shells.
Wetlands Ecol Manage (2008) 16:219–236 221
123
Fish were collected for diet analysis using a beach
seine. In the long-term monitoring surveys (1999–
2001), California halibut were collected using two
blocking nets and a bag seine (13.3 m long and 2.1 m
deep) with a 3 mm mesh. At each site, blocking nets
were deployed to confine all fish within a known area.
The bag seine was then swept in the area between the
two blocking nets across the channel to the opposite
bank. Passes were repeated (typically 3–4 sweeps)
until the catch neared depletion levels in the area
between the nets. All halibut in the catch were
counted and measured.
Daily food consumption (Daily ration)
On each sampling date (Table 1), California killifish,
topsmelt and California halibut were collected with a
beach seine every 3 h over a 24-h period, preserved
in 95% ethanol in the field, then transferred to 70%
ethanol in the laboratory. California killifish were
sampled on various occasions (Table 1) to include
days when daytime tidal heights were sufficient to
inundate the marsh surface and provide fish with
access to the inundated habitat, and also on days
when tidal heights were insufficient to flood the
marsh surface (no marsh access).
Topsmelt were sampled in Tijuana Estuary
(Table 1) to evaluate their feeding patterns in an
estuarine system that has remained consistently open
to tidal flushing. Topsmelt were also sampled in Los
Penasquitos Lagoon (Table 1), a system that fre-
quently gets impounded due to tidal inlet closures, in
order to quantify the effects of lagoon impoundment
on their food consumption patterns. Daily feeding
patterns of topsmelt in Los Penasquitos Lagoon were
quantified on two separate occasions in March 1999,
(1) when the tidal inlet to the lagoon was completely
blocked with sand and cobble, impounding the
lagoon, and (2) when the tidal inlet to the lagoon
was subsequently scoured open by high surf events.
California halibut were sampled at two locations in
Tijuana Estuary, the mouth site and the seacoast site
(Fig. 1, Table 1), in order to quantify their daily food
consumption in channels with different habitat char-
acteristics. While similar size classes of each fish
species were chosen for food consumption analysis
on each sampling date, two distinct size classes of
Fig. 1 Location of coastal
wetland sampling sites in
southern California
222 Wetlands Ecol Manage (2008) 16:219–236
123
California halibut (small sized juveniles = 108–
135 mm TL and large sized juveniles = 190–
250 mm TL) were additionally sampled at the
Seacoast site in Tijuana Estuary (Table 1) to assess
size-specific differences in daily food consumption
levels of juvenile halibut.
For each fish species, gut fullness for each 3-h
period was determined by measuring (mm, total
length, TL) and weighing (g, wet weight) from 5 to
15 fish, then dissecting out and weighing the entire
gut. Food weights in the guts were estimated as the
difference between total gut and empty gut weights
(EGW). Empty gut weights were estimated from
previously determined regressions of EGW on fish
body mass. Gut evacuation rates were calculated by
fitting appropriate mathematical curves (Post 1990) to
the decline in gut contents during the night when
feeding had ceased (indicated by empty anterior
digestive tracts). Gut evacuation rates (E, h-1) were
combined with time-specific estimates of gut-fullness
(Ft, g/g) to yield daily food consumption (DFC, g/g/
d), based on the method of Elliott and Persson (1978):
DFC =Eh
1�e� Ehð Þ
X9
t¼1
Ftþ1 � Fte� Ehð Þ
� �
where h represents the time interval (3 h) between
gut fullness estimates, and t represents each of the
nine time periods when gut fullness was determined.
Ninety-five percent confidence intervals (CI) were
estimated for each daily food consumption value by
pooling the standard errors of each of the nine 3-h
point estimates of gut fullness on a sampling date,
using the method described by Madon (1998).
Data on tidal hydroperiods for each of the sampling
dates were obtained from water level records published
by the National Oceanic and Atmospheric Adminis-
tration (NOAA; http://tidesandcurrents.noaa.gov/).
Table 1 Sampling sites, dates, number of fish used in diet analysis and size ranges for fish collected in Tijuana Estuary (TJE) and
Los Penasquitos Lagoon (LPL)
Fish species Estuary Sampling site Sampling dates No. of fish (N) Fish size range (mm)
California killifish LPL Mouth October 1–2, 1998 59 41–93
TJE Mouth October 29–30, 1998 85 48–76
TJE Mouth October 12–13, 1999 92 38–75
TJE Mouth October 27–28, 1999 124 40–74
TJE Mouth November 16–17, 1999 112 31–79
Topsmelt LPL Mouth* March 11–12, 1999 90 140–192
LPL Mouth� March 29–30, 1999 113 133–197
TJE Mouth October 29–30, 1998 129 132–190
TJE Mouth March 13–14, 1999 121 118–184
TJE Seacoast August 5–6, 1999 87 120–175
TJE Mouth October 27–28, 1999 115 132–190
California halibut TJE Seacoast August 5–6, 1999 51 108–135
TJE Seacoast August 5–6, 1999 45 190–250
TJE Mouth October 27–28, 1999 48 95–120
TJE Mouth November 16–17, 1999 54 98–118
TJE Mouth Every May, June, September
and December between 1995–1999
76! 5–120!
TJE Seacoast Every May, June, September
and December between 1995–1999
392! 8–498!
TJE East-West Every May, June, September
and December between 1995–1999
19! 9–125!
Symbols indicate that the collection of topsmelt occurred during a natural experiment on days when the tidal inlet to LPL was closed
(*) and open (�) to tidal flushing. California halibut were sampled for diet analysis and were also collected as part of a long-term
biological monitoring effort in Tijuana Estuary to be used for site-specific size distribution analysis in this study (!)
Wetlands Ecol Manage (2008) 16:219–236 223
123
Diet composition—topsmelt
A weighted index of relative importance (IRI, Pinkas
et al. 1971) was used to characterize the importance
of common prey categories in topsmelt diets. Ran-
domly chosen subsamples of 30–60 gastrointestinal
tracts of topsmelt collected in each of the six diel
samples (Table 1) were dissected and contents were
counted and identified to the lowest taxonomic level
possible. Prey items were grouped to form general
taxonomic categories (e.g., algae, copepods, amphi-
pods) for the IRI analyses. The volume of small prey
items was determined by flattening the gut contents to
a uniform thickness of 1 mm on a clear Petri dish
placed over graph paper, estimating the area (mm2),
then volume (mm3) of each prey group (Hyslop 1980;
Rozas and LaSalle 1990; West et al. 2003). The
volume of larger prey items was measured as the
volume of water displaced by the prey items in a
graduated 10-ml (+0.1 ml) cylinder. The IRI was
calculated for each sampling date (Table 1) as:
IRI ¼ % N + % Vð Þ �% FO
where N is the prey number, V is the prey volume and
FO is the frequency of occurrence of each prey
category. A %IRI value was then calculated for each
prey category by dividing the summed IRI value of
the prey item by the total IRI value of all prey items
(West et al. 2003).
Bioenergetics modeling of fish growth potential
A bioenergetics approach was used to estimate the
growth potential of California killifish and California
halibut under a range of environmental conditions.
Growth of California killifish on each of the sampling
dates was predicted with a killifish bioenergetics
model developed and independently validated by
Madon et al. (2001). The bioenergetics model is
based on an energy budget where specific growth rate
(dB/Bdt) is modeled as:
dB
Bdt¼ C � ðRþ F þ UÞ
where B is the weight of the fish, t is time, C is
consumption, R is respiration, F is egestion, and U is
excretion. The model predicts killifish growth on a
daily basis using food consumption and water
temperature as model inputs (Madon et al. 2001)
and was used to predict the growth of a 55 mm
killifish (2 g wet weight) based on inputs of field
estimates of killifish food consumption and water
temperature measured in this study.
Energy budgets developed for California halibut
acclimated to a range of salinities and water temper-
atures (Madon 2002) were used to predict its growth
under a range of salinities (5–35) and water temper-
atures (10–30�C). Growth contours were generated
for small (26 g wet mass, 120 mm TL) and large
juvenile halibut (200 g wet mass, 270 mm TL) over a
range of salinities and water temperatures at low and
high levels of prey availability. Low prey availability
reflected prey levels where halibut of a specific size
consumed only 25% of its maximum daily ration;
high prey availability reflected food consumption
levels of 75% of the maximum daily ration (Madon
2002). Growth contours were used to evaluate the
potential effects of episodic salinity and water
temperature changes caused by tidal inlet closures
on the growth of small and large juvenile halibut.
Energy budgets (Madon 2002) were also used to
predict the specific growth rates of juvenile Califor-
nia halibut at the Mouth and Seacoast sites in Tijuana
Estuary. Specific growth rates of juvenile California
halibut were predicted at ambient water temperatures
and at 20�C using field estimates of daily food
consumption measured for halibut sampled at the
Mouth and Seacoast sites in August, October and
November of 1999.
Results
Daily food consumption (Daily ration)
California killifish in Tijuana Estuary displayed
crepuscular feeding patterns with gut fullness peaking
during twilight hours on the two sampling periods
(October 12–13, 1999 and October 27–28, 1999)
when daytime tides were sufficiently high to provide
fish with access to the marsh surface (Fig. 2). The
feeding peaks followed peak high tides on both these
sampling occasions. In contrast, feeding activity of
killifish remained at relatively low levels throughout
each of the three 24-h sampling periods (October 1–2,
1998, in Los Penasquitos Lagoon, and October 29–
30,1998 and November 16–17, 1999, in Tijuana
Estuary) when tidal heights were insufficient to
224 Wetlands Ecol Manage (2008) 16:219–236
123
provide fish with marsh access (Fig. 2). Gut fullness
during each of the sampling periods without marsh
access never exceeded 0.024 g/g, in contrast to gut
fullness of fish with marsh access which peaked at
0.04 -0.05 g/g (Fig. 2).
Daily food consumption by killifish with access to
the marsh surface was two to five times higher than in
killifish that were restricted to feeding in subtidal
channels (Fig. 3). Field estimates of daily ration in
fish with marsh access ranged from 0.274 + 0.025 g/g
(27.4 + 2.5% body weight) to 0.329 + 0.024 g/g, and
were significantly higher compared to daily rations of
0.064 + 0.045 g/g to 0.132 + 0.021 g/g in fish with-
out marsh access (Fig. 3).
Crepuscular feeding patterns were also observed in
topsmelt sampled in Tijuana Estuary, and peaks in
gut fullness followed peak daytime high tides,
regardless of sampling location and date (Fig. 4).
Daily food consumption by topsmelt in Tijuana
Estuary varied significantly between sampling dates
and ranged from 0.216 + 0.035 g/g/d (21.6 + 3.5%
body weight; + 95% CI) to 0.589 + 0.032 g/g/d
(Fig. 5).
Topsmelt were also sampled in Los Penasquitos
Lagoon over a 24-h period when the lagoon was
impounded due to closure of the tidal inlet, and again
when the lagoon was open to tidal flushing due to
scouring of the tidal inlet by high surf. During March
11–12, 1999 when the lagoon was impounded and
closed to tidal circulation, topsmelt feeding occurred
at low levels and did not show distinct peaks in
feeding activity, as indicated by gut fullness. Gut
fullness during this period never exceeded 0.045 g/g
(Fig. 6). In contrast, when the lagoon was open to
Fig. 2 Daily food consumption cycles (bold dark lines) of
California killifish (31–93 mm, total length, TL range) at
Tijuana Estuary and Los Penasquitos Lagoon in relation to daily
tidal cycles (dotted lines). For each time period, food consump-
tion is given in terms of the average food mass (+1 standard
error, SE) observed in the guts of a sample of killifish. The
horizontal dotted black line indicates the tidal height relative to
mean low low water (MLLW) required for marsh access. Bold
dark bars below the x-axis signify post-dusk and nighttime hours.
N is the number of fish sampled on each date
Fig. 3 Field estimates of daily amounts of food consumed
(+95% confidence limits, CI) by California killifish at Tijuana
Estuary (TJE) and Los Penasquitos Lagoon (LPL) on days with
and without marsh access. N is the number of fish sampled on
each date
Wetlands Ecol Manage (2008) 16:219–236 225
123
tidal circulation as indicated by the distinct tidal
patterns observed on March 29–30, 1999, topsmelt
resume normal feeding patterns with a distinct peak
in gut fullness (0.103 g/g) following the daytime
peak in high tide (Fig. 6).
Daily food consumption by topsmelt was approx-
imately twice as high when the lagoon was open to
tidal circulation, compared to when the lagoon was
impounded and lacked tidal influence (Fig. 7). Daily
ration of topsmelt under impounded conditions
(0.124 + 0.030 g/g/d) was the lowest among all
food consumption levels observed in topsmelt under
normal tidal patterns (0.216 + 0.035 to 0.589 +
0.032 g/g/d) in Tijuana Estuary and Los Penasquitos
Lagoon (Figs. 5, 7).
Small juvenile California halibut (95–135 mm,
TL) at the Seacoast and Mouth sites in Tijuana
Estuary showed distinct peaks in gut fullness that
coincided with daytime peaks in high tide (Fig. 8).
Fig. 4 Daily food
consumption cycles (bold
dark lines) of topsmelt
(118–190 mm, total length,
TL range) at Tijuana
Estuary in relation to daily
tidal cycles (dotted lines;
tides are in relation to mean
low low water, MLLW).
For each time period, food
consumption is given in
terms of the average food
mass (+1 standard error,
SE) observed in the guts of
a sample of topsmelt. Bold
dark bars below the x-axis
signify post-dusk and
nighttime hours. N is the
number of fish sampled on
each date
Fig. 5 Field estimates of daily amounts of food consumed
(+95% confidence limits, CI) by topsmelt at Tijuana Estuary
(TJE), 1998–1999. N is the number of fish sampled on each
date
Fig. 6 Daily food consumption cycles (bold dark lines) of
topsmelt in Los Penasquitos Lagoon on two days in March
1999, when the tidal inlet was closed and then subsequently
open to tidal flushing. For each time period, food consump-
tion is given in terms of the average food mass (+1 standard
error, SE) observed in the guts of a sample of topsmelt. Daily
tidal cycles are indicated by dotted lines, relative to mean low
low water (MLLW) and reveal the lack of a tidal cycle within
the lagoon when the inlet was closed. The bold dark bars
signify post-dusk and nighttime hours. N is the number of fish
sampled on each date and TL is total length range of fish
sampled
226 Wetlands Ecol Manage (2008) 16:219–236
123
Daily rations of small juvenile halibut at these sites
ranged from 0.104 + 0.011 to 0.136 + 0.018 g/g/d,
but did not differ significantly between sampling
dates (Fig. 9). Conversely, feeding level of large
juvenile halibut (190–250 mm, TL) at the Seacoast
site was significantly low throughout the 24-h period,
compared to feeding activity of small juveniles
(Fig. 8). Daily ration of large juvenile halibut at the
Seacoast site was at least an order of magnitude lower
than that of small juveniles collected on the same
sampling date (August 5–6, 1999) (Fig. 9).
Diet composition
Algae was the most important food item in topsmelt
diets in Tijuana Estuary with an IRI of 68.4%,
significantly higher than all other prey categories
(Fig. 10, One-way ANOVA; F6,21 = 13.2, P \0.001). Tukey’s HSD test revealed that there were
no significant differences in % IRIs of copepods,
amphipods, insects, digested matter, sand and ‘‘other’’
prey categories (P [ 0.05) which ranged from 0.2%
to 14.4% (Fig. 10). The ‘‘other’’ prey category mostly
consisted of bivalve, cyprid and gastropod veligers,
small gastropods, ostracods, oligochaetes, crabs lar-
vae, and isopods, of which none exceeded an IRI of
1% in topsmelt diet.
Fig. 7 Field estimates of daily amounts of food consumed
(+95% confidence limits, CI) by topsmelt in Los Penasquitos
Lagoon on days when tidal inlet was closed, and then
subsequently open to tidal flow between the ocean and the
lagoon. N is the number of fish sampled on each date
Fig. 8 Daily food consumption cycles (bold dark lines) of
small (95–135 mm, TL) and large (190–250 mm, TL) juvenile
California halibut at study sites within Tijuana Estuary in
relation to daily tidal cycles (dotted lines, tides are in relation
to mean low low water, MLLW). For each time period, food
consumption is given in terms of the average food mass
(+1 standard error, SE) observed in the guts of a sample of
halibut. The bold dark bars signify post-dusk and nighttime
hours. N is the number of fish sampled on each date and TL is
total length range of fish sampled
Wetlands Ecol Manage (2008) 16:219–236 227
123
Under normal tidal patterns when the inlet of Los
Penasquitos Lagoon was open to the tidal flushing,
diet composition of topsmelt was similar to that of
topsmelt in Tijuana Estuary. That is, algae dominated
topsmelt diet at 83.8% IRI and copepods, amphipods,
insects, digested matter, sand and ‘‘other’’ prey
categories ranged from an IRI of 0.7% to 3.6%
(Fig. 11). Topsmelt diet composition, however,
changed dramatically under conditions when the
lagoon was impounded due to closure of the tidal
inlet. Under impounded conditions, topsmelt diets
consisted mainly of copepods, sand, and digested
unidentifiable matter (IRIs ranging from 14.7% to
44.2%), with algae contributing to only a small
fraction of the diet (IRI = 0.8%, Fig. 11).
Bioenergetics modelling of fish growth potential
Bioenergetic model predictions of specific growth
rates of California killifish with marsh access ranged
from 0.132 + 0.016 g/g/d (13.2 + 1.6% body weight/d)
to 0.174 + 0.015 g/g/d, and were significantly higher
compared to growth rates of 0.002 + 0.028 g/g to
0.049 + 0.013 g/g in fish without marsh access
(Fig. 12). The model predicted positive specific
growth rates for killifish in Tijuana Estuary at all
levels of food consumption tested; however, killifish
would lose weight (specific growth rate = -0.026 g/g/d)
at its lower range of estimated food consumption in
Los Penasquitos Lagoon (Fig. 12).
Contours of specific growth rates of small
(Fig. 13) and large juvenile halibut (Fig. 14) show
areas of growth and weight loss across a range of
water temperatures and salinities. When prey
Fig. 9 Field estimates of daily amounts of food consumed
(+95% confidence limits, CI) by large (dark bar) and small
(light bars) juvenile California halibut at the Seacoast and
Mouth sites in Tijuana Estuary, 1999. N is the number of fish
sampled on each date
Fig. 10 Mean (+1 SE)% dietary index of relative importance
(IRI) of food items observed in guts of topsmelt (128–190 mm,
total length) from Tijuana Estuary
Fig. 11 Percent dietary index of relative importance (IRI) of
food items observed in guts of topsmelt (133–197 mm, total
length) in Los Penasquitos Lagoon during March 1999 on days
when the tidal inlet was closed, and then subsequently opened
to tidal circulation between the ocean and the lagoon
Fig. 12 Growth rates of California killifish with and without
marsh access in Los Penasquitos Lagoon (LPL) and Tijuana
Estuary (TJE), predicted with a killifish bioenergetics model
developed by Madon et al. (2001)
228 Wetlands Ecol Manage (2008) 16:219–236
123
availability is high (food consumption level = 75%
of maximum consumption), small halibut can grow
across almost the entire ranges of water temperature
and salinity tested, except at water temperatures of
29�C and above and at very low water temperature
and salinity conditions where weight loss occurs
(Fig. 13a). Under low prey availability (food con-
sumption level = 25% of maximum consumption),
the upper water temperature limit at which weight
loss occurs drops to approximately 28�C; below 17�C,
weight loss also occurs across the entire range of
salinities tested (Fig. 13b).
Large juvenile halibut grow between water tem-
peratures of approximately 16�C and 22�C across the
entire range of salinities tested when prey availability
is high; weight loss occurs in large juvenile halibut
below and above this water temperature range across
all salinities (Fig. 14a). Under low prey availability,
large juvenile halibut can grow only in a very narrow
range of water temperatures (19–21�C) and salinities
(27–35 ppt), and generally experience weight loss
under a broad range of environmental conditions
(Fig. 14b).
The effect of tidal inlet closure on the water
temperature and salinity of Los Penasquitos Lagoon
is illustrated for the time period between March 15
and 29, 1998 (Fig. 15). During periods when the tidal
inlet was open (March 15–March 18), water temper-
atures and salinities in LPL averaged approximately
19�C and 31 ppt, respectively (Fig. 15). The tidal
inlet partially closed on March 18 and was com-
pletely obstructed by March 19. In the period
following closure of the tidal inlet, water temperature
and salinity dropped sharply and then stabilized at
approximately 14�C and 6 ppt, respectively (Fig. 15).
Growth contours indicate that under water tem-
peratures and salinities typical of pre-closure
environmental conditions in Los Penasquitos Lagoon,
specific growth rates of small juvenile halibut would
range between 0.005 and 0.01 g/g/d when food
Fig. 13 Growth rates of small juvenile halibut (26 g wet
mass) in Los Penasquitos Lagoon under (a) high prey
availibility conditions and (b) low prey availability conditions,
predicted using energy budgets developed for halibut by
Madon (2002). Red dots indicate growth potential of halibut
under open and closed tidal inlet conditions within the lagoon
Fig. 14 Growth rates of large juvenile halibut (200 g wet
mass) in Los Penasquitos Lagoon under (a) high prey
availability conditions and (b) low prey availability conditions,
predicted using energy budgets developed for halibut by
Madon (2002). Red dots indicate growth potential of halibut
under open and closed tidal inlet conditions within the lagoon
Wetlands Ecol Manage (2008) 16:219–236 229
123
availability was high, and between 0 to 0.002 g/g/d
under low prey availability conditions (Fig. 13a, b).
However, under post-closure conditions, small hali-
but would experience weight loss regardless of prey
availability (Fig. 13a, b). Similarly, at high prey
availability, large juvenile halibut would grow at a
rate of approximately 0.006 g/g/d under pre-closure
conditions but begin to lose weight under post-
closure conditions (Fig. 14a). Under low prey avail-
ability, large juvenile halibut experience would
experience slight weight loss under pre-closure
conditions, but would rapidly begin to lose weight
under post-closure conditions (Fig. 14b).
Based on field estimates of daily food consumption
in Tijuana Estuary, specific growth rates of small and
large juvenile California halibut at the Seacoast site
(August 5–6, 1999) differed significantly at the ambi-
ent water temperature (24�C) and at 20�C (Fig. 16).
Energy budgets predicted that small juvenile halibut
would have specific growth rates of approximately
0.055 + 0.008 g/g/d at the Seacoast site in contrast to
large juveniles which would lose weight on average
(Fig. 16). At the Mouth site, energy budgets for small
juvenile halibut predicted specific growth rates ranging
from 0.040 + 0.005 to 0.047 + 0.005 g/g/d, depending
on water temperature, sampling date and field esti-
mates of food consumption (Fig. 16).
California halibut size distributions and channel
characteristics
Quarterly sampling for juvenile halibut was conducted
at three sites with different channel characteristics
every year between 1995 and 2001 as part of a long-
term biological monitoring effort at Tijuana Estuary.
Juvenile halibut were present at all three sites. At the
shallow ‘‘Mouth’’ site and the ‘‘East-West Channel’’
site, the sizes of juvenile halibut ranged between
5 mm and 125 mm, TL. No halibut exceeding
125 mm TL was found at the Mouth and East-West
Channel sites in the 28 sampling events that occurred
between 1995 and 2001 (Fig. 17). Summer water
temperatures at the Mouth and East-West Channel
sites often exceed the lethal limit (28�C) for large
juvenile halibut ([200 mm TL, Madon 2002), but
water temperatures and salinities at these sites
(Fig. 18) were within the ranges tolerated by smaller
juveniles (Madon 2002). Conversely, the large, deep,
Seacoast site was the only one where large juvenile
halibut exceeding 200 mm TL were collected fre-
quently (Fig. 17). Water temperatures at the Seacoast
site never exceeded, and were substantially lower
than the lethal limit for large juvenile halibut
(Fig. 18).
Discussion
California killifish
The marsh surface clearly plays an important ecolog-
ical role in the life history of the California killifish,
Fundulus parvipinnis, which depend on marsh access
Fig. 15 The effects of tidal inlet closure and rainfall on water
temperature (solid line, circles) and salinity (broken line,
triangles) in Los Penasquitos Lagoon, March 15–29, 1998
Fig. 16 Specific growth rates (+95% confidence limits, CI) of
small and large juvenile halibut at 20�C and ambient water
temperatures (shown in figure) on specific dates and sites in
Tijuana Estuary. Growth rates were predicted using field
estimates of food consumption and energy budgets developed
for juvenile halibut (Madon 2002)
230 Wetlands Ecol Manage (2008) 16:219–236
123
during high tides to support their feeding and growth.
The marsh surface also plays a similar ecological role
for the mummichog, F. heteroclitus, in Atlantic Coast
estuaries by providing trophic connectivity between
subtidal and intertidal habitats (Weisberg and Lotrich
1982; Kneib 1986). In contrast to subtidal channels,
the marsh surface floods only intermittently, thereby
limiting access to invertebrate predators and allowing
invertebrate food resources to build up between
periods of inundation (Kneib 1997). The marsh
surface also supports high densities of surface-dwell-
ing invetebrate prey that are otherwise not available or
abundant in subtidal channels (Kneib 1997; West and
Zedler 2000).
Using baited minnow traps in a southern Califor-
nia estuary, West and Zedler (2000) have shown that
California killifish will access the marsh surface
during spring high tides and that the coastal marsh
provides a rich foraging area for this species.
Analysis of killifish guts revealed that killifish with
marsh access had gut fullness indices that were as
much as six times higher than in fish restricted to
creek habitats (West and Zedler 2000). Madon et al.
(2001) subsequently used the killifish gut fullness
data collected by West and Zedler (2000) in a
bioenergetics model to show that killifish could
potentially grow from 20–100% faster if they add
intertidal marsh surfaces to their subtidal feeding
areas. These two studies (West and Zedler 2000;
Madon et al. 2001) were based on single point
estimates of gut fullness, and neither directly mea-
sured the food consumption of California killifish
over 24-h periods when fish were restricted to
Fig. 17 Size distributions of juvenile halibut at the three
sampling sites in Tijuana Estuary, 1995–2001. N is the total
number of fish sampled at each site and TL is total length range
of fish sampled
Fig. 18 Seasonal average
water temperatures and
salinities measured at the
three sampling sites in
Tijuana Estuary during
March (M), June (J),
September (S) and
December (D), 1995–2001.
The dotted line in each
panel indicates the lower
limit of lethal water
temperature (28�C) for
large juvenile halibut,
which is often reached or
exceeded in the shallow and
mid-sized channels during
summer months
Wetlands Ecol Manage (2008) 16:219–236 231
123
subtidal channels and compared those to daily food
consumption estimated during periods when high
tides provided killifish access to the marsh surface.
This study is the first to provide direct field evidence
that killifish can increase their daily food intake by
two- to five-fold by feeding on the marsh surface.
Furthermore, this study also shows that increased
levels of feeding on the marsh surface translate into
growth rates that are up to two orders of magnitude
higher than growth rates of fish restricted to feeding
in subtidal channels. This study offers strong and
direct field evidence that supports two previous
studies (West and Zedler 2000; Madon 2001) on
the functional benefits of marsh surface access to
California killifish, as well as studies on its Atlantic
coast congener, F. heteroclitus (Weisberg et al. 1981;
Weisberg and Lotrich 1982; Kneib 1986).
Tidal inlet closures and increased marsh surface
elevations due to sedimentation are common prob-
lems in the coastal wetlands of southern California
(Zedler 2001; Callaway and Zedler 2004; Wallace
et al. 2005) and have direct implications for killifish
feeding and growth. High tides are essential for
inundation of the marsh surface and for facilitating
the movement of California killifish from subtidal
channels to the marsh plain. During high tides, field
observations have shown that killifish use the
extensive marsh-creek connectivity offered by natu-
ral ‘‘tidal creek networks’’ to access the marsh
surface from subtidal areas; that is, they move from
deeper subtidal channels into connecting smaller
channels and tidal creeks to gain access to the
interior marsh surface (Desmond et al. 2000). If the
tidal inlet were to close, fish access to the marsh
surface would be restricted as the coastal wetland
would no longer be under tidal influence and would
lack the tidal elevations necessary to inundate the
marsh surface. Sediment accretion on the marsh plain
would also have the effect of restricting fish access to
the marsh surface. High sedimentation rates would
lead to an increase in marsh surface elevations,
which over time, could reduce marsh inundation
periods or even completely restrict the flooding of
the marsh surface under extreme cases of sedimen-
tation. In either case (tidal inlet closure or
sedimentation), marsh access for killifish could be
restricted, confining killifish to subtidal channels
which appear to be sub-optimal in terms of support-
ing killifish feeding and growth.
In light of the implications of tidal inlet closures
on killifish feeding and growth, coastal restoration
projects must ensure that their restoration designs
incorporate hydrologic and structural elements that
are conducive to maintaining an open tidal inlet.
Coastal wetland management plans must also incor-
porate specific actions that include the prompt
removal of sand, sediment and cobble blocking tidal
inlets. For example, Los Penasquitos Lagoon has a
management plan that specifically involves the
clearing of debris, sand, cobble and sediment from
the blocked inlet with a bulldozer. A sediment
management plan that is aimed at controlling the
input of excessive sediment into coastal wetland
areas is also necessary. The Tijuana River National
Estuarine Research Reserve, as part of its phased
program to restore salt marshes in degraded upland
areas that were historically wetlands, has recently
built basins to capture and retain large volumes of
sediment that may otherwise be deposited into
adjacent salt marsh areas. However, these basins are
sometimes overwhelmed by the sheer volume of
sediment that gets deposited during winter storm
events, resulting in sediment bypassing the basins and
subsequently depositing in the salt marsh areas.
Finally, restoration plans must incorporate tidal
creek networks into the design of coastal wetlands
(Madon et al. 2002; Wallace et al. 2005). Tidal creek
networks will provide sufficient marsh surface-creek
connectivity required by fish for marsh surface access
during high tide events. In southern California,
excavation of deep basins or deep channels within
areas of filled wetlands is allowed by resource
agencies as compensatory mitigation for damages to
fish habitat (Zedler et al. 1997; Zedler 2001). The
marsh-water interface in these constructed wetlands
is greatly reduced and these wetlands bear little
structural or functional resemblance to the tidal creek
networks characteristic in natural coastal wetlands
(Zedler 1996a; West and Zedler 2000). Tidal creek
networks can be excavated in restoration sites or
measures can be taken to at least jump-start their
development (Wallace et al. 2005). For example,
tidal creek networks designed after a natural tidal
drainage network were excavated into an 8-ha
experimental salt marsh in Tijuana Estuary and
played an important role in aiding the further
development of a drainage network comparable to
reference systems in 4–5 years (Wallace et al. 2005).
232 Wetlands Ecol Manage (2008) 16:219–236
123
Excavating these drainage networks is, however,
costly and other methods to jump-start the process of
tidal network formation have been suggested. These
include the manipulation of elevation gradients and
location of vegetation plantings so that erosion can be
promoted along unplanted corridors to eventually
form tidal creeks (Wallace et al. 2005), using kelp
amendments in wetland soils to reduce soil bulk
density and counteract soil compaction to promote
the erosive formation of creeks (Wallace et al. 2005),
building internal peninsulas in graded restoration
sites to guide hydrologic inundation and drainage
patterns which eventually lead to channel and creek
formation, and making shallow excavations to jump-
start creek formation (Williams 2001; Williams et al.
2002).
Topsmelt
Daily food consumption and diet composition of
topsmelt, Antherinops affinis, both appear to be
influenced by tidal patterns and tidal inlet closures.
Under normal 24-h tidal patterns in an estuary with
an unobstructed tidal inlet (Tijuana Estuary), top-
smelt exhibit diel feeding patterns with peak feeding
following daytime high tides. Daily rations of
topsmelt in Tijuana Estuary ranged from approxi-
mately 22% to 59% of body weight, and macroalgae
(primarily Enteromorpha sp.) dominated topsmelt
diets. The high degree of herbivory exhibited by
topsmelt in Tijuana Estuary appears to be common in
this species; large topsmelt ([100 mm, comparable
to topsmelt sizes in this study) in other California
bays and estuaries are also known to forage almost
exclusively on macroalgae (Horn and Allen 1985;
Barry et al. 1996). Topsmelt have pharyngeal jaws
which they likely use to lyse algal cells; high amylase
activity in their guts allows them to extract and
assimilate nutrients and energy from algae with high
efficiency (Logothetis et al. 2001). High levels of
food consumption by topsmelt (up to 59% of body
weight) also point to an algae-rich diet. Macroalgae
have low protein content and are relatively hard to
break down and assimilate, requiring herbivorous fish
to compensate by maintaining high levels of food
intake (Horn et al. 1999).
Los Penasquitos Lagoon, like most coastal wet-
lands in southern California, experiences frequent
tidal inlet closures. This study shows that such
closures have a negative impact on feeding by
topsmelt. One such tidal inlet closure event and the
subsequent opening of the inlet in March 1999
allowed quantification of topsmelt feeding in the
impounded lagoon. Food consumption rate of top-
smelt was 50% lower when the tidal inlet was
closed, compared to when the lagoon was under tidal
influence. Under impounded conditions and lack of a
tidal pattern in the lagoon, topsmelt did not show any
distinct peaks in feeding activity and maintained low
levels of feeding throughout the 24-h period. Algae
was not the dominant food item in topsmelt diet,
which instead exhibited a higher proportion of sand,
digested matter and copepods under impounded
conditions. When the lagoon subsequently opened
to tidal flushing, topsmelt resumed their normal
feeding patterns with a characteristic peak in
daytime feeding activity following high tide and
macroalgae dominating the diet, much like the
populations of topsmelt in Tijuana Estuary. Mainte-
nance of an open tidal inlet and promoting
unrestricted tidal flow between the ocean and lagoon
are important management actions that are necessary
to support the health of topsmelt populations in
coastal wetlands.
California Halibut
Paralichthys californicus are also adversely affected
by tidal inlet closures. In southern California, tidal
inlet closures are particularly common during the
winter (November–March) when offshore storms
accumulate sand, cobble and debris near the inlet
and restrict or prevent tidal flow between the ocean
and the lagoon or estuary. Water temperature and
salinity changes rapidly in these impounded wetlands,
particularly during precipitation events and could
adversely affect growth of juvenile California halibut.
Small juvenile halibut appear to be well adapted to
variable estuarine conditions (Madon 2002), but may
still be impacted by sudden and dramatic fluctuations
in water temperature and salinity in these impounded
systems during the winter. For example, the tidal inlet
closure that occurred in Los Penasquitos Lagoon
during March 1998 resulted in sharp declines in water
temperature and salinity within the impounded
lagoon. Growth contours of halibut indicate that
Wetlands Ecol Manage (2008) 16:219–236 233
123
small juveniles would lose body mass under these
impounded conditions, regardless of prey availability.
Large juvenile halibut are relatively intolerant of
variable water temperatures and salinities, and their
growth would likely be more adversely impacted by
tidal inlet closures. Growth contours reveal that even
when the tidal inlet is open, large juvenile halibut
appear to lose some body mass when prey availability
is low. Tidal inlet closures occur more frequently
during winter months, often coinciding with periods
when prey densities (e.g., arrow gobies, Clevelandia
ios), are typically at their lowest levels compared to
other times of the year (West et al. 2003). Reduced
levels of prey availability, combined with sharp
variations in water temperature and salinity induced
by tidal inlet closures would prove to be particularly
stressful for large juvenile halibut and lead to rapid
weight loss.
Tidal creek networks consisting of channels and
creeks of various orders are also important to halibut
and should be incorporated into restoration designs
for coastal wetlands. Large juvenile halibut occupy
only deeper, higher order channels while small
halibut are abundant in both low and high order
channels. High order channels may primarily func-
tion as thermal refugia for large juvenile halibut, but
likely offer little food support. In Tijuana Estuary,
large juvenile halibut were only present at the
Seacoast site, which is located in a broad, deep
channel (a high order channel) where water temper-
atures typically remain below the lethal temperature
for large juvenile halibut. However, daily food
consumption of large juvenile halibut at the Seacoast
site was very low and below levels required to
support significant growth. Quarterly monitoring of
fish conducted between 1997–2001 in low and high
order channels in Tijuana Estuary reveal that densi-
ties of C. ios, the primary prey of juvenile halibut
(West et al. 2003), were frequently lower in higher
order channels compared to low order channels
(M. Cordrey and J. West 2003, Pacific Estuarine
Research Laboratory, San Diego State University,
CA, personal communication). Densities of gobies in
high order channels could conceivably fall below
prey thresholds necessary for supporting growth of
large juvenile halibut (Madon 2002). Alternately, the
arrow goby is a small-sized fish and may no longer
be energetically efficient as a food source for large
juvenile halibut.
Conclusions: guidelines for managing and
restoring impacted coastal wetlands
This study provides an in-depth analysis of the effects
of common environmental stressors such as tidal inlet
closures, sedimentation events and water quality
variations on ecological function of key components
of the fish community in the coastal wetlands of
southern California. By focusing on species exhibit-
ing a range of life histories and occupying different
trophic positions within the fish community, mean-
ingful insights are gained into, (1) how environmental
stressors affect ecological function in coastal wet-
lands and, (2) how these results can be used to
provide guidance on the appropriate management and
restoration of these valuable ecosystems.
In conclusion, this study underscores the impor-
tance of implementing the specific management and
restoration activities in coastal wetlands, based on an
evaluation of the effects of anthropogenic stressors on
the fish community:
• Maintenance of an open tidal inlet, either through
physical clearance of materials blocking the inlet
and/or through the careful design and engineering
of the tidal inlet in restoration plans.
• Incorporating tidal creeks into the restoration
design, either through excavation or through
implementation of various measures that can
jump-start their natural development.
• Restoration designs should include specific ele-
ments to ensure that tidal creeks are adjacent to
intertidal salt marsh habitats to facilitate fish
access to the marsh surface.
• Restoration designs should incorporate tidal creek
networks consisting of creeks of various orders to
support diversity in ecological function. For
example, large, deep higher order creeks may
provide thermal refuge for juvenile fish but will
also contain higher densities of fish predators and
lower food resources, compared to shallower low
order creeks. Even with a specific fish species
(e.g., California halibut), individuals may parti-
tion the use of these tidal creek networks based on
size. For example, small juvenile halibut primar-
ily use shallow, small creeks (low order) for
refuge from predation and feeding, whereas larger
juveniles use deeper, high order creeks and
channels for thermal refuge.
234 Wetlands Ecol Manage (2008) 16:219–236
123
• Management plans need to be developed and
implemented to curtail excessive input of sedi-
ment into coastal wetlands, which can have
negative effects on the fish community ranging
from acute (mortality of biota) to subtle (rise in
marsh surface elevations which reduces march
access to fish).
Acknowledgements This study was supported by funding
provided by the Earth Island Institute and the National Science
Foundation (NSF Award DEB 0212005) while the author was
at the Pacific Estuarine Research Laboratory, San Diego State
University. CH2M HILL, Inc. also provided support in time
and materials to the author through an initiative grant for data
analysis and writing. John Callaway, Janelle West, Michelle
Cordrey, Michael Kiener, Brian Weller, Michelle Bowman,
Kecia Kerr and Gregory Williams assisted with field sampling
and data collection efforts. Thanks are due to Joy B. Zedler for
her guidance and support throughout this study. Thanks are
also due to the staff at the Tijuana River National Estuarine
Research Reserve and the Los Penasquitos Lagoon Foundation
for supporting this research. This paper is dedicated to the
memory of Khorshed Shyam Verma.
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