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22001166 SOUTHEASTERN NATURALIST 1V5o(4l.) :1651,3 N–6o3. 04
Analysis of the Nearshore Fish Community in a Northeast
Florida Estuary
Ed McGinley1,*, Austin O’Connor1, Esme Vazquez1, and Jessica Veenstra1
Abstract - The Guana Tolomato Matanzas National Estuarine Research Reserve
(GTMNERR), located in Northeast Florida, serves as an ideal estuarine habitat for many
economically and ecologically important species of fish and crabs. As climate change affects
Florida ecosystems, the replacement of Spartina alterniflora (Smooth Cordgrass)
marshes by northward-moving mangroves is possible. A change in the dominant vegetation
has the potential to alter organic carbon inputs, which can lead to a shift in the primary and
secondary consumers in the area. An assessment of the fish community is needed in the
systems where the change from Smooth Cordgrass to mangrove is the most likely in order
to determine which species and which breeding populations will be affected. We conducted
a biodiversity survey over the course of 24 months to document the seasonal and spatial
patterns in species richness, seasonal abundance, and size of species caught. From May
2013 to April 2015, we used a 15.24-m seine net to sample 8 sites within the GTMNERR.
Comparable to many other estuaries, the catch per unit effort and species richness decreased
in the colder winter months and rose through spring and summer. Temperature was the
main factor that controlled the species assemblage, with some species recorded only during
certain months of the year, while salinity was a minor parameter. Certain species were
correlated with colder seasons, i.e., Leiostomus xanthurus (Spot) juveniles and Menidia
spp. (silverside), or negatively correlated with other species, i.e., Spot and Fundulus similis
(Longnose Killifish). Temperature and species interactions can be useful in tracking specific
populations and the effects of anthropogenic influences in this system.
Introduction
Due to the productive nature of estuarine systems, these areas are invaluable for
many species of fish and invertebrates (Paperno et al. 2001). These areas provide
habitat, feeding grounds, and nursery areas for both migrant and resident species
(Gilmore et al. 1982, Kerr et al. 2010, Purtlebaugh and Allen 2010). Seasonal variation
in Florida estuaries has been observed in other studies (Gorecki and Davis
2013, Tremain and Adams 1995, Turtora and Schotman 2010), although the degree
of seasonal change may be a factor of location.
Northeast Florida represents an ecotone between Spartina alterniflora (Loisel)
(Smooth Cordgrass)-dominated saltmarsh and mangroves migrating northward.
Three mangrove species—Avicennia germinans (L.) (Black Mangrove), Rhizophora
mangle (L.) (Red Mangrove), and A. marina (Forssk) (White Mangrove)— have
been documented extending their range northward at a migration rate ranging from
1.3 to 4.5 km yr-1 (Williams et al. 2014). A change in the dominant vegetation can
1Department of Natural Sciences, Flagler College, 74 King Street, St. Augustine, FL 32084.
*Corresponding author - emcginley@flagler.edu.
Manuscript Editor: Paul Leberg
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have effects on the organic material available (Osborne et al. 2007) and, in turn,
directly shape the fish communities present (Mazmuder et al. 2005, Robertson and
Duke 1987). A biomonitoring effort needs to be in place because these changes are
happening rapidly and could effect a shift in the primary and secondary consumers
in an area.
The Guana Tolomato Matanzas National Estuarine Research Reserve
(GTMNERR; Fig. 1) consists of 300 km2 of coastal land within Northeast Florida.
This reserve is a collaborative effort between the Department of Environmental
Protection and NOAA, with the main goal to foster research and stewardship.
This area is ideal for monitoring aquatic communities because of accessibility to a
Figure 1.
Map of the
study sites
in Northeast
Florida.
Sites
are numbered
1–8
from north
to south.
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multitude of habitats including oyster beds, saltmarsh, and mangroves. This is also
a highly flushed system (Webb et al. 2007), which means harmful algal blooms
that plague many other coastal systems are a rare occurrence here. However, fishmonitoring
efforts in this area have been sporadic, with no other multi-site efforts
currently taking place. Turtora and Schotman (2010) performed a fish-seine survey
and otter-trawl survey from November 2001 to March 2005 within northeast estuaries
from St. Augustine (St. Johns County) south to Ponce Inlet (Flagler County).
This effort, along with a yearlong trawl survey (M. Kimball, University of South
Carolina Baruch Institute, Georgetown, SC, unpubl. data ), represents the majority
of fish monitoring that has taken place in this study area.
Multiple factors are known to affect fish distributions in estuaries and include,
but are not limited to, temperature (Turtora and Schotman 2010), salinity (Barletta
et al. 2005), dissolved oxygen (Maes et al. 2004), and nitrate concentration
(Gutierrez-Estrada et al. 2008). Although these parameters are often tested to help
predict fish biodiversity or abundance, the importance of each depends on the estuary
in question. Therefore, it is important to collect data on multiple aspects of the
system in order to determine what are the abiotic and biotic parameters driving
the fish community.
Because this system has a multitude of different habitats, and represents an
ecotone between saltmarsh and mangroves, a monthly seine survey was initiated in
May 2013 to document the fish and swimming-crab assemblage. This study is the
first step towards filling a knowledge gap related to fish communities in this area.
Because this is an ongoing project, it can help to identify and document any fish
community changes in the coming years.
Methods
Study sites
The GTMNERR is split into northern and southern sections, with the city of St.
Augustine in the middle (Fig. 1). A total of 8 sites were sampled during this study
within and just outside the boundaries of the GTMNERR. Two sites were located in
the northern section of the GTMNERR, 3 sites were located within the city limits of
St. Augustine, and 3 sites were located in the southern section of the GTMNERR.
Habitat characterization
The estuaries of Northeast Florida are dominated by intertidal saltmarsh comprised
of Smooth Cordgrass (Dame et al. 2000), although sporadic mangroves are
encountered and have been documented moving northward into the area (Williams
et al. 2014). For each sampling site, using Google Earth Pro, we defined the width
of the habitat characterization area as 25 m parallel to the shoreline on each side of
the GPS location for the site, and the uppermost boundary for the habitat characterization
area as a sea wall (if present) or the upland forest edge. We determined
the average slope of the habitat area by using an optical survey level, a stadia rod,
and a transect line to find the change in elevation over distance for a transect line
perpendicular to the shoreline from the sea wall (if present) or the upland forest
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edge to a safe wading depth in the water (usually 10–20 m from the lower salt marsh
vegetation edge). Using a Petri dish, we collected surface-sediment samples from 2
areas: adjacent to the salt marsh vegetation edge and 10 m down from the salt marsh
vegetation edge. Sediment particle size was determined using sieves with mesh
sized for very fine sand (0.63 μm) and fine gravel (2000 μm). If there was variation
between the particle sizes of 2 samples at each site, we reported 2 particle-size classifications.
Additionally, we determined percent organic matter of the sediments
using the loss-on-ignition method outlined in Wang et al. (2011). The area of salt
marsh vegetation at the site as well as the distances to the nearest inlet, road, building,
boat ramp, and dock were found through satellite-photo analysis (Fig. 2). We
calculated an average distance to anthropologic influences by averaging all of the
distances to the nearest road, building, boat ramp, and dock. In this region, natural
subtidal structural complexity is limited, as the benthic sediments are generally
fine, and there have been no observations of submerged aquatic vegetation (Sargent
et al. 1995, Turtora and Schotman 2010) or subtidal oyster beds in this region. Thus,
much of the natural structural complexity of a site in this region is in the intertidal
zone, and defined by salt marsh vegetation and oyster beds. Additionally, anthropogenic
structures, such as piers or docks, contribute to both intertidal and subtidal
structural habitat complexity. We report the presence or absence of such structures
in Table 1.
Sampling methods
Starting May 2013, we sampled each of the sites monthly with the assistance
of undergraduate volunteers from Flagler College (St. Augustine, FL). A 15.24 m
x 1.2 m beach seine with 6.4-mm mesh was deployed by having one person walk
straight out into the waterway while the second person remained at the land–water
interface. The net was always moved against the current in order to make sure
Figure 2. Example
of satellite-photo
analysis: (A) GPS
point and site number,
(B) habitat
characterization
area (25 m on either
side of GPS point),
(C) polygon encompassing
vegetation
area of site, (D)
distance to nearest
road, (E) distance
to nearest building,
(F) distance to nearest
inlet (extends
off image), (G) distance to nearest dock, and (H) distance to nearest public boat ramp (extends
off image) (image source: Google Earth.)
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the net was fully extended in the water column. Once the entire seine was deployed,
it was stretched in a semi-circle pattern back to shore taking care to make sure the
net was pulled tight to prevent fish from jumping over the top of the net. This procedure
was done twice at each site, with the second pull occurring above or below the
section that was sampled with the first pull (whatever was possible at the specific
site). We placed all fish and crabs from the first pull in an aerated buc ket to ensure
they were not recaptured during the second seine pull. Organisms were identified
by student volunteers, and identifications were verified by the lead author before
being recorded. We also measured total length (mm) of all specimens captured.
Specimens that we were unable to identify in the field were either taken back to the
lab, photographed, or documented in a species complex, i.e., Eucinostomus spp.
(mojarra), silverside, etc. We used a dissecting microscope at 30x magnification
to study organisms taken back to the lab. We photographed unknown species and
sent these pictures to researchers at the Florida Fish and Wildlife Commission for
assistance in identification.
After 2 seine pulls were completed, we recorded water temperature and dissolved
oxygen at each site using an YSI PRO dissolved oxygen probe (YSI Incorporated,
Yellow Springs, OH), and measured salinity with a refractometer (Extech Instruments:
Wilmington, NC). All water-quality measurements were taken in close
proximity to the where the seine was pulled, taking care that all measurements were
conducted outside of the sediment plume caused by the seine pul ls.
Statistical analyses
For each site, we calculated a catch per unit effort (CPUE). Because the water
height was not measured during sampling, this calculation represents an average of
the number of fish caught per seine pull per site.
We ordinated all sites, using nonmetric multidimensional scaling (NMDS) to
identify spatial or temporal patterns in the fish community data. While NMDS is
Table 1. The different measures of habitat characterization of the 8 sites that have been consistently
sampled throughout the study. Veg. = vegetation, anthro. = anthropogenic.
Avg Presence
Avg sand Distance Avg Presence of inter- or
shell content Avg to distance to of subtidal
Veg. Avg content (63μm– % nearest anthro. intertidal anthro.
area % (>2000 μm) 2000μm) organic inlet influences oyster structural
Site # (m2) slope (mass %) (mass %) matter (km) (km) beds complexity
1 1968 7 0 93 2.7 12.9 5.8 Yes* No
2 1202 14 0 77 0.8 10.6 4.4 Yes No
3 0 18 1 98 2.3 1.8 0.6 No Yes
4 0 8 6 92 0.7 2.9 1.1 Yes* No
5 2234 5 14 77 1.6 10.1 3.6 No No
6 121 8 3 94 0.7 9.0 2.0 No Yes
7 1168 19 0 95 0.7 1.5 0.9 No No
8 151 25 15 82 4.4 7.1 1.6 No No
*Artificial oyster reefs were installed at these sites.
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not a statistical test, it is a useful tool in providing a visual representation of site
similarity. We overlayed the abiotic factors of temperature and salinity on the ordination
to determine if they could explain the scattering of the sampling sites. Only
taxa with abundances greater than 25 individuals were included in this analysis to
prevent rare species from obscuring the results. As part of the ordination, we used
the package envfit in the statistical program R (R Development Core Team 2008) to
determine which species were correlated with the ordination axe s.
We used linear regression to determine if salinity and/or temperature were
instrumental in influencing taxa richness and catch per unit effort. The null hypothesis
was that neither variable influenced catch per unit effort or taxa richness. We
evaluated assumptions for linear regression using R with tests for normality of the
residuals, multi-collinearity, and homoscedasticity. Because catch per unit effort
was several orders of magnitude greater between the smallest catch and the largest
catch, we performed a log transformation on these data.
We ran a correlation analysis on species abundance to determine species groupings.
Because the abundance data was non-normal, we calculated a Kendall’s tau
between the 9 most common species. Because all sites were grouped together for
this analysis, it is possible to see if certain groupings of species were commonly
seen together. The null hypothesis in this case was that no species were correlated
with each other at the sampling sites.
Results
A total of 40,080 individuals were collected from May 2013 through April 2015
(no sampling was conducted during July 2014). The dominant species in order of
abundance were Leiostomus xanthurus (Spot) (n = 13,036; 32.5%), Anchoa mitchilli
(Bay Anchovy) (n = 12,085; 30.2% of total), Gerreidae spp. (mojarra) (n = 3308;
8.3%), Menidia spp. (silverside) (n = 2622; 6.5%), Anchoa hepsetus (L.) (Broadstriped
Anchovy) (n = 1965, 4.9%), and Mugil spp. (mullet) (n = 1458; 3.6%).
Of the 303 fish and crab species that have been documented in the GTMNERR
(Frazel 2009), 89 species were captured and identified during this study. This number
is lower than what was documented by Frazel (2009) due to our grouping individuals
that we found to be impossible to resolve beyond the genus in the field, as well as only
using a seine net rather than seine and otter trawl (Turtora and Schotman 2010). For
26 of these 89 different species, we captured only a single individual.
Species richness and abundance
We compared the variables collected that describe the various sites to the species
seen at each site to determine if certain species were selecting sites based on
these parameters (Table 1). No apparent patterns were detected when comparing
these data. One interesting finding did emerge: shrimp (taxonomy not identified in
this study) were associated with sites that have intertidal oyster reefs. These sites
included 2 man-made oyster reefs and 1 natural oyster reef.
The average taxa richness changed throughout the year (Fig. 3). The number of
species present in the Matanzas River Estuary follows a similar monthly pattern
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over the 2 years of this study. The taxa richness for 2013 peaked in June (9.7 ±
1.34), and then steadily declined throughout the rest of the year. The taxa richness
was lowest in January 2014 (2.38 ± 0.53), and then began to increase from month
to month, peaking in 2014 in May (10.11 ± 1.43) as well as August (10.14 ± 1.53).
The pattern is similar to 2013, as the taxa richness decreased through the fall and
winter, hitting a low in December 2014 (4.25 ± 1.89). Taxa richness again began
to increase as the months progressed in 2015. It should also be noted the standard
deviations were much higher from November 2014 through April 2015 (mean =
2.19) versus November 2013 through April 2014 (mean = 0.79).
Temperature varied seasonally during this survey. Highest temperatures were
seen during the end of spring (30.12 ± 1.34 °C) and into the summer months (August;
29.17 ± 1.87 °C). Salinity during this experiment was much more variable
than temperature. The recorded values depended on the stage of the tide during
sampling rather than the season. Overall, salinities ranged from 18 to 43 ppt, and
there was no seasonal component to the salinities measured. It should be noted that
only 1 salinity measurement was below 20 ppt, and 146 of the 173 recorded salinities
were above 30 ppt.
While Turtora and Schotman (2010) indicate they recorded salinity during their
study, no values were reported. Therefore, salinity data from 2002 through 2014
were accessed through the National Estuarine Research Reserve System Centralized
Data Management Office (NOAA National Estuarine Research Reserve
System 2012). Data sondes recorded salinity every 30 minutes from 2002 through
2007, and every 15 minutes after 2007 at 2 sites close to where the current project
Figure 3. Average species richness by month during the study. Error bars represent 1 standard
deviation around the mean. No sampling was conducted in Ju ly 2014.
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took place. A total of 676,418 observations of salinity were recorded during this
12-year period, and 95% of the observations were above 30 ppt. These data indicate
that this system receives very little freshwater input and maintains a high salinity
measurement, which could indicate why this parameter was not useful in predicting
the fish community.
The taxa richness and catch per unit effort were compared with salinity and
temperature to determine if either abiotic factor could explain the variation seen
throughout this study. The models indicated that neither temperature (P = 0.34) nor
salinity (P = 0.64) explained the variation seen in the log-transformed catch per
unit effort. When these 2 variables were used to construct a model to explain taxa
richness, only temperature was statistically significant (P < 0.0001), while salinity
was not (P = 0.06). Dissolved oxygen was not included in this model because it was
highly correlated with temperature.
Certain species were correlated with different seasons during this study (Table 2).
Out of the most abundant species, Spot and juvenile Mullet tended to be correlated
with the months January through May (NMDS axis 1 and 2; Fig. 4). Silverside
tended to be most abundant September through March, but were still present in other
months. Mojarra were most abundant in the estuary May through December. Both
anchovy species had a more sporadic pattern: present in summer (May through June)
and then sparse in samples throughout the rest of the year (Fig. 5).
Figure 4. NMDS ordination of sample locations from May 2013 to April 2015, ordinated by
the fish community recorded at each site. The temperature vector is scaled in the direction
in which it is significantly correlated with sites. Stress level for the NMDS was 0.28.
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Species’ relative abundance were also correlated with each other during this
study. Spot were significantly negatively correlated with both mojarra (-0.62)
and Fundulus similis (Longnose Killifish) (-0.45). Bay Anchovy were positively
correlated with Broad-striped Anchovy (0.35) and Alosa sapidissima (American
Shad) (0.33) and negatively correlated with silverside (-0.39), and Longnose Killifish
(-0.35). Mojarra were negatively correlated with mullet species (-0.32),
whereas silverside were positively correlated with Longnose Killifish. Broadstriped
Anchovy were positively correlated with American Shad, which means
that both anchovy species tended to be caught with American Shad, while silverside
and Longnose Killifish were caught together. The other 2 most populous
Table 2. Correlations of taxa abundance along NMDS axis 1 and 2 for sites ordinated by fish community
data (2D solution, stress =0.28; Fig. 2).
Species Correlation Abundance (%)
NMDS axis 1
Leiostomus xanthurus -0.97 32.52
Anchoa mitchilli 0.99 30.15
Eucinostomus spp. 0.99 8.25
Mugil spp. -0.64 3.64
Brevoortia tyrannus -0.76 0.88
Fundulus heteroclitus -0.86 0.63
Opisthonema oglinum 0.73 0.39
Fundulus majalis -0.95 0.38
Trachinotus falcatus 0.94 0.30
Ctenogobius boleosoma -0.99 0.10
Lutjanus synargis 0.58 0.07
NMDS axis 2
Menidia menidia -0.95 6.54
Anchoa hepsetus 0.94 4.90
Mugil spp. -0.77 3.64
Alosa sapidissima 0.92 1.99
Fundulus similis -0.99 1.47
Callinectes sapidus 0.90 0.94
Callinectes similis 0.99 0.94
Brevoortia tyrannus -0.65 0.88
Mugil curema -0.89 0.72
Lagodon rhomboides 0.99 0.66
Callinectes spp. 0.89 0.53
Anchoa spp. 0.88 0.46
Opisthonema oglinum 0.68 0.39
Fundulus spp. -0.86 0.22
Citharichthys spp. 0.88 0.14
Poecilia latipinna -0.86 0.10
Chloroscombrus chrysurus 0.92 0.08
Sciaenops ocellatus -0.99 0.07
Lutjanus synargis 0.81 0.07
Mugil cephalus 0.98 0.07
Caranx spp. 0.89 0.05
Sphoeroides maculatus -0.89 0.05
Paralichthys albigutta 0.92 0.03
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species, Spot and mojarra, were negatively correlated with each other, indicating
they were rarely caught together.
This estuarine system is used by multiple species as a nursery area. Spot collected
during this study show a seasonal trend of growth during the sampling period.
Small individuals (15–25 mm) were collected in December and January (Fig. 5),
and the average size collected increased throughout the year. Spot were absent
from the nearshore community in the months leading up to the appearance of the
small juveniles (October through December). Seasonal patterns of abundance were
observed for juveniles of other species as well, i.e., Trachinotus falcatus (Permit)
and mullets.
Non-native species
During this study, only 1 non-native species was found during all of the sampling
events: Charybdis hellerii (Indo-Pacific Swimming Crab). This species was
only found at 1 site, the Castillo de San Marcos in downtown St. Augustine. The
species has been documented in this water body before (Frazel 2009). Seven total
individuals were captured: two in July 2013, three in November 2013, one in May
2014, and one in June 2014. Because this is a non-native species, all individuals
Figure 5. Log-transformed catch per unit effort for the 6 most abundant species recorded
during this study. No sampling was conducted in July 2014. The difference in catch per unit
effort at sites was often several orders of magnitude different, and a transformation of the
data was needed.
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captured were euthanized under guidance from the Florida Fish and Wildlife Conservation
Commission. The largest individual caught was 54 mm, and the average
was 27.29 ± 4.65 mm.
Discussion
The GTMNERR nearshore community in Northeast Florida had highest abundances
of lower trophic level fish and a high species richness during this study that
was influenced by seasonal changes, congruent with the findings with a previous
study in this area (Turtora and Schotman 2010). The sampling in this region of
Florida was dominated by a few species, with a total of 89 taxa sampled.
Turtora and Schotman (2010) collected these same species during their study
in this system from 2002 to 2004. The most numerically dominant species found in
their study were Bay Anchovy (32% out of a total of 358,446 sampled individuals),
Spot (16%), Micropogonias undulatus (Atlantic Croaker) (5%), mojarra (4.7%),
and Broad-striped Anchovy (3.9%). These species represent the same dominant
assemblage caught during the present study with one notable exception: Atlantic
Croaker. A total of only 9 Atlantic Croaker were caught during this current study.
However, Turtora and Schotman (2010) found Atlantic Croaker were an abundant
species during their sampling, which included both seine pulls and otter trawls. In
their seine pulls, 5700 Atlantic Croaker were captured, which represented 2.1% of
the total catch. Further research will be needed to determine why this species was
not as abundant in our survey as previously observed.
Catch per unit effort revealed that higher numbers of fish were caught in warmer
spring and summer months. The increase in catch follows a pattern of increasing
water temperatures, indicating that season is a strong variable that affects the abundance
and species richness observed during the year (Allen 1982, McErlean et al.
1973). The pattern of high species richness and abundance of individuals in spring
and summer, and low values in the winter is a common theme seen in estuarine
ecosystems throughout the world (Akin et al. 2005).
The species richness also decreased during the colder months. This is common
in many other estuaries, including the Indian River Lagoon, FL, where species
tend to migrate away during the winter months to deeper water (Tremain and Adams
1995), possibly to spawn (Gilbert 1986). Tzeng and Wang (1992) found that
dominant species had distinct times of the year in which recruitment was occurring
in a Taiwan estuary. Spot juveniles were present in the colder months (January and
February), while mojarra, as well as anchovy numbers were low during that time of
year. Silverside were the dominant species from November to March, again when
mojarra and anchovy were at lower numbers. As Tzeng and Wang (1992) suggest,
this finding could be indicative of the most efficient use of limited resources in
this system. Abundance studies will need to be coupled with an analysis of diet to
determine the degree of niche overlap of these species in this system.
Temperature and salinity were both tested as parameters to explain catch per unit
effort and taxa richness of the nearshore fish community. Only temperature was a
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significant factor that influenced the taxa richness recorded. This result was most
likely due to seasonal changes in the estuary. Turtora and Schotman (2010) found
that the fish community observed in their seine samples in this system were also
influenced by seasonal changes. This pattern is not uncommon in estuarine systems,
as the fish community will often change as the water temperature changes and
species grow and/or migrate (Baird and Ulanowicz 1989, Rakocinski et al. 1992,
Tremain and Adams 1995).
One species that exhibited a pronounced seasonal abundance was Spot. Spot
young-of-the-year entered the estuary in December into January. They represented
one of the most numerically dominant species present during this time, until their
numbers tapered off by mid-summer. This pattern is mirrored very closely in the
Indian River Lagoon (Tremain and Adams 1995). Numerically, Spot were dominant
starting in February and then tapered off in mid-summer. Estuaries along the east
and Gulf coast frequently provide nursery areas for Spot (Chao and Musick 1977,
Rooker et al. 1998, Warlen and Burke 1990).
Paralichthys lethostigma (Southern Flounder) follows a similar pattern to Spot.
Adults migrate offshore during the colder winter months, starting in December and
will breed during this time; the larvae are transported back into the estuaries to
metamorphose after 30–60 days (Daniels 2000). Twenty-three Southern Flounder
juveniles were captured during this study during the months of March through May
and had an average size of 43.6 ± 17.3 mm. This is a small sample size, but indicates
this could be an important nursery for more species than just Spot. A more in-depth
analysis of specific fish populations would be needed to determine the relative importance
of this estuary as a source of recruitment for various populations.
The Matanzas River Estuary has a minimal freshwater input compared to
other systems, and therefore, salinity was not a significant factor in influencing
the number of species or catch per unit effort in this estuary. Although this system
is classified as an estuary, the salinity changes are not as pronounced as in other
estuarine systems. The salinities in 84% of the sampling events were above 30 ppt,
including for both low and high tide sampling that occurred throughout the calendar
year. Although salinity is known to be a major influence on fish assemblages
(Barletta et al. 2005, Rakocinski et al. 1992), it did not appe ar to influence the fish
community in the Matanzas River Estuary.
Several species that could not be identified in the field were grouped into species
complexes, i.e. silverside, mojarra, etc. There were 2 reasons for our inability
to accurately identify the individual to the species level: we could not see small
distinguishing characters in the field, and there is the possibility of hybridization. It
has been known for some time that several species in Northeast Florida are capable
of hybridizing (Duggins et al. 1995, Gonzalez et al. 2009). In the future, DNA barcoding
will help to resolve identification issues.
The Indo-Pacific Swimming Crab was the only non-native species captured
during our sampling. The crab seems to be less common in this system, as we only
found it at 1 site, in downtown St. Augustine. There are records of its presence
in the Matanzas River Estuary (Frazel 2009). A previous study of this non-native
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in the Indian River Lagoon (Dineen et al. 2001) indicate that this species prefers
structure, and was rarely seen away from these type of areas. In many cases, little
is known about the population status of this species beyond that it is now present
in an area.
The GTMNERR system sampled in this study has high species richness, an
abundant food source of lower trophic level taxa, and ample habitat to allow for
fish nurseries. A continuous long-term biomonitoring effort will be needed going
forward to document the effects of climate change, northward migration of mangroves,
and possible invasion of non-native species. It will also be necessary to
construct food webs for the species in this area to determine linkages among the
inhabitants of this system.
Acknowledgments
Many students and faculty have made this project possible along the way. We are indebted
to C. Adams, and A. Panaro for helping to start this project as well as C. van Kuiken,
R. Morrissey, R. Rolland, A. Palmer, S. Elliot, J. Cepdea, F. Rowel, H. Tuggle, D. Pariser,
M. Musante, A. Castle, C. Herbert, and T. Considine for volunteering their time. We are
also grateful for the insights and ideas provided by M. Brown and assistance from the NPS
by K. Foote. G. Merovich was instrumental in teaching statistical methods. Data was supplied
by the Guana Tolomato Matanzas National Estuarine Research Reserve monitoring
program and N. Dix, and all sampling was done with permits supplied by the Florida FWC
(SAL-13-1472D-SR) and Florida DEP (05061313).
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Appendix 1. List of species captured and their relative percent of the total. Naming authority
and common names are provided for each species.
Individuals Relative
Species caught percent
Leiostomus xanthurus (Lacepède) (Spot) 13,036 32.52
Anchoa mitchilli (Valenciennes in Cuvier & Valenciennes) (Bay 12,085 30.15
Anchovy)
Eucinostomus spp.(mojarra) 3308 8.25
Menidia spp.(silversides) 2622 6.54
Anchoa hepsetus (L.) (Broad-striped Anchovy) 1965 4.90
Mugil spp. (mullet) 1458 3.64
Alosa sapidissima (Wilson) (American Shad) 797 1.99
Shrimp 664 1.66
Fundulus similis (Baird and Girard) (Longnose Killifish) 588 1.47
Callinectes sapidus Rathbun (Blue Crab) 378 0.94
Callinectes similis Williams (Lesser Blue Crab) 378 0.94
Brevoortia tyrannus (Latrobe) (Atlantic Menhaden) 352 0.88
Mugil curema Valenciennes (White Mullet) 289 0.72
Lagodon rhomboides (L.) (Pinfish) 266 0.66
Fundulus heteroclitus (L.) (Mummichog) 254 0.63
Callinectes spp. (swimming crabs) 214 0.53
Anchoa spp. (anchovies) 185 0.46
Opisthonema oglinum (Lesueur) (Atlantic Thread Herring) 157 0.39
Fundulus majalis (Walbaum) (Striped Killifish) 152 0.38
Trachinotus falcatus (L.) (Permit) 122 0.30
Fundulus spp. (killifish) 87 0.22
Citharichthys spp. (whiffs) 55 0.14
Ctenogobius boleosoma (Jordan and Gilbert) (Darter Goby) 40 0.10
Poecilia latipinna (Lesueur) (Sailfin Molly) 39 0.10
Chloroscombrus chrysurus (L.) (Atlantic Bumper) 31 0.08
Sciaenops ocellatus (L.) (Red Drum) 29 0.07
Lutjanus synagris (L.) (Lane Snapper) 28 0.07
Mugil cephalus L. (Striped mullet) 28 0.07
Paralichthys lethostigma Jordan and Gilbert (Southern Flounder) 26 0.06
Caranx hippos (L.) (Crevalle Jack) 25 0.06
Citharichthys spilopterus Günther (Bay Whiff) 24 0.06
Lutjanus griseus L. (Gray Snapper) 24 0.06
Pomatomus saltatrix L. (Bluefish) 24 0.06
Bathygobius soporator (Valenciennes) (Frillfin Goby) 23 0.06
Bairdiella chrysoura (Lacépède) (Silver Perch) 21 0.05
Sphoeroides maculatus (Bloch and Schneider) (Northern Puffer) 21 0.05
Ctenogobius spp. (Gobies) 19 0.05
Synodus foetens (L.) (Inshore Lizardfish) 19 0.05
Cyprinodon variegatus Lacépède (Sheepshead Minnow) 17 0.04
Albula vulpes (L.) (Bonefish) 12 0.03
Paralichthys albigutta Jordan and Gilbert (Gulf Flounder) 12 0.03
Symphurus plagiusa (L.) (Black-cheek Tonguefish) 12 0.03
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Individuals Relative
Species caught percent
Prionotus spp. (searobins) 10 0.02
Strongylura notata (Poey) (Redfin Needlefish) 10 0.02
Trachinotus carolinus (L.) (Florida Pompano) 10 0.02
Elops saurus L. (Ladyfish) 9 0.02
Micropogonias undulates (L.) (Atlantic Croaker) 9 0.02
Charybdis hellerii (Milne-Edwards) (Indo-Pacific Swimming Crab) 7 0.02
Caranx latus Agassiz (Horse-eye Jack) 6 0.01
Ctenogobius smaragdus (Valenciennes) (Emerald Goby) 5 0.01
Cynoscion nebulosus (Cuvier in Cuvier and Valenciennes) (Spotted 5 0.01
Seatrout)
Haemulon spp. (grunts) 5 0.01
Stephanolepis hispidus (L.) (Planehead Filefish) 5 0.01
Lolliguncula brevis (Blainville) (Atlantic Brief Squid) 4 0.01
Prionotus scitulus Jordan and Gilbert (Leopard Searobin) 4 0.01
Gymnura micrura (Bloch and Schneider) (Smooth Butterfly Ray) 3 0.01
Menippe mercenaria (Say) (Florida Stone Crab) 3 0.01
Microgobius gulosus (Girard) (Clown Goby) 3 0.01
Sciaenid (drums) 3 0.01
Achirus lineatus (L.) (Lined Sole) 2 0.005
Chilomycterus schoepfi (Walbaum) (Striped Burrfish) 2 0.005
Paralichthys spp. (sand flounders) 2 0.005
Paralichthys dentatus (L.) (Summer Flounder) 2 0.005
Strongylura marina (Walbaum) (Atlantic Needlefish) 2 0.005
Syngnathus louisianae Günther (Chain Pipefish) 2 0.005
Trinectes maculatus (Bloch and Schneider) (Hogchoker) 2 0.005
Ablennes hians Valenciennes (Flat Needlefish) 1 0.002
Centropristis striata L. (Black Sea Bass) 1 0.002
Chaetodipterus faber (Broussonet) (Atlantic Spadefish) 1 0.002
Dasyatis Sabina (Lesueur) (Atlantic Stingray) 1 0.002
Diplectrum bivittatum (Valenciennes) (Dwarf Sand Perch) 1 0.002
Gambusia spp. (mosquitofish) 1 0.002
Gobionellus oceanicus (Pallas) (Highfin Goby) 1 0.002
Gobiesox punctulatus (Poey) (Stippled Clingfish) 1 0.002
Labrisomus nuchipinnis (Quoy and Gaimard) (Hairy Blenny) 1 0.002
Menticirrhus americanus (L.) (Southern Kingfish) 1 0.002
Mentichirrus littoralis (Holbrook) (Gulf Kingfish) 1 0.002
Oligoplites saurus (Bloch and Schneider) (Leatherjack) 1 0.002
Orthopristis chrysoptera (L.) (Pigfish) 1 0.002
Prionotus carolinus (L.) (Northern Searobin) 1 0.002
Prionotus tribulus Cuvier (Bighead Searobin) 1 0.002
Chelonia mydas (L.) (Green Sea Turtle) 1 0.002
Selene vomer (L.) (Lookdown) 1 0.002
Sphoeroides spengleri (Bloch) (Bandtail Puffer) 1 0.002
Sphoeroides testudineus (L.) (Checkered Puffer) 1 0.002
Sphyraena guachancho Cuvier (Guachanche Barracuda) 1 0.002
Stephanolepis setifer (Bennett) (Pygmy Filefish) 1 0.002
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Individuals Relative
Species caught percent
Stomatopoda (mantis shrimp) 1 0.002
Syngnathus spp. (pipefish) 1 0.002
Syngnathus floridae (Jordan and Gilbert) (Dusky Pipefish) 1 0.002
Syngnathus fuscus Storer (Northern Pipefish) 1 0.002
Syngnathus scovelli (Evermann and Kendall) (Gulf Pipefish) 1 0.002
Unknown 53 0.13
Total 40,080 100