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Analysis of the Nearshore Fish Community in a Northeast Florida Estuary
Ed McGinley, Austin O’Connor, Esme Vazquez, and Jessica Veenstra

Southeastern Naturalist, Volume 15, Issue 4 (2016): 613–630

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Southeastern Naturalist 613 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 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 Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 614 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. Southeastern Naturalist 615 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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 Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 616 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.) Southeastern Naturalist 617 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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. Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 618 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 Southeastern Naturalist 619 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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. Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 620 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. Southeastern Naturalist 621 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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 Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 622 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. Southeastern Naturalist 623 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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 Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 624 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 Southeastern Naturalist 625 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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). Literature Cited Akin, S., E. Buhan, K.O. Winemiller, and H. Yilmaz. 2005. Fish assemblage structure of Koycegiz Lagoon-Estuary, Turkey: Spatial and temporal distribution patterns in relation to environmental variation. Estuarine, Coastal, and Shelf Scien ce 64:671–684. Allen, L.G. 1982. Seasonal abundance, composition, and productivity of the littoral fish assemblage in upper Newport Bay, California. 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Clark, A.H. Hines, S.A. Reed, and H.P. Walton. 2001. Life history, larval description, and natural history of Charybdis hellerii (Decapoda, Brachyura, Portunidae), an invasive crab in the Western Atlantic. Journal of Crustacean Biology 21:774–805. Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 626 Duggins, C.F., Jr., A.A. Karlin, T.A. Mousseau, and K.G. Relyea. 1995. Analysis of a hybrid zone in Fundulus majalis in a northeastern Florida ecotone. Heredity 74:1 17–128. Frazel, D.W. 2009. Site profile of the Guana Tolomato Matanzas National Estuarine Research Reserve. Ponte Vedra, FL. 151pp. Gilbert, C.R. 1986. Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (South Florida)—Southern, Gulf, and Summer Flounders. US Fish and Wildlife Service Biological Report 82(11.54). US Army Corps of Engineers, Vicksburg, MS. TR EL-82-4. 27 pp. Gilmore, R.G., D.W. Cooke, and C.J. Donohoe. 1982. 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Maes, J., S. Van Damme, P. Meire, and F. Ollevier. 2004. Statistical modeling of seasonal and environmental influences on the population dynamics of an estuarine fish community. Marine Biology 145:1033–1042. Mazmuder, D., N. Saintilan, and R.J. Williams. 2005. Temporal variations in fish catch using pop nets in mangrove and saltmarsh flats at Towra Point, NSW, Australia. Wetlands Ecology and Management 13:457–467. McErlean, A.J., S.G. O’Connor, J.A. Mihursky, and C.I. Gibson. 1973. Abundance, diversity, and seasonal patterns of estuarine fish populations. Estuarine and Coastal Marine Science 1:19–36. NOAA National Estuarine Research Reserve System (NERRS). 2012. System-wide Monitoring Program. Data accessed from the NOAA NERRS Centralized Data Management Office website. Available online at http://www.nerrsdata.org/. Accessed 12 October 2012. Osborne, T.Z., P.W. Inglett, and K.R. Reddy. 2007. The use of senescent plant biomass to investigate relationships between potential particulate and dissolved organic matter in a wetland ecosystem. Aquatic Botany 86: 53–61 Paperno, R., K.J. Mille, and E. Kadison. 2001. Patterns in species composition of fish and selected invertebrate assemblages in estuarine subregions near Ponce de Leon Inlet, Florida. Estuarine, Coastal, and Shelf Science 52:117–130. Purtlebaugh, C.H., and M.S. Allen. 2010. Relative abundance, growth, and mortality of five age-0 estuarine fishes in relation to discharge of the Suwannee River, Florida. Transactions of the American Fisheries Society 139:1233–1246. R Development Core Team. 2008. R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. Available online at http:// www.R-project.org. Southeastern Naturalist 627 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 Rakocinski, C.F., D.M. Baltz, and J.W. Fleeger. 1992. Correspondence between environmental gradients and the community structure of marsh-edge fish in a Louisiana estuary. Marine Ecology Progress Series 80:135–148. Robertson, A.I., and N.C. Duke. 1987. Mangroves as nursery sites: Comparisons of the abundance and species composition of fish and crustaceans in mangroves and other nearshore habitats in tropical Australia. Marine Biology 96:193–205. Rooker, J.R., S.A. Holt, M.A. Soto, and G.J. Holt. 1998. Postsettlement patterns of habitat use by sciaenid fishes in subtropical seagrass meadows. Estuarie s 21:318–327. Sargent, F.J., T.J. Leary, D.W. Crewz, and C.R. Kreur. 1995. Scarring of Florida’s seagrasses: Assessment and management options. FMRI Tech. Rept. TR-1/ Florida Marine Research Institute, St. Petersburg, FL Tremain, D.M., and D.H. Adams. 1995. Seasonal variations in species diversity, abundance, and composition of fish communities in the northern Indian River Lagoon, Florida. Bulletin of Marine Science 57:171–192. Turtora, M., and E.M. Schotman. 2010. Seasonal and spatial distribution patterns of finfish and selected invertebrates in coastal lagoons of northeastern Florida, 2002–2004. US Geological Survey, Reston, VA. Tzeng, W.N., and Y.T. Wang. 1992. Structure, composition, and seasonal dynamics of the larval and juvenile fish community in the mangrove estuary of Tanshui River, Taiwan. Marine Biology 113:481–490. Wang, Q., Y. Li, and Y. Wang. 2011. Optimizing the weight loss-on-ignition methodology to quantify organic and carbonate carbon of sediments from diverse sources. Environmental Monitoring and Assessment 174:241–257. Warlen, S.M. and J.S. Burke. 1990. Immigration of larvae of fall/winter spawning marine fishes into a North Carolina estuary. Estuaries 13:453–461. Webb, B.M., J.N. King, B. Tutak, and A. Valle-Levinson. 2007. Flow structure at a trifurcation near a North Florida inlet. Continental Shelf Research 27: 1528–1547 Williams, A.A., S.F. Eastman, W.E. Eash-Loucks, M.E. Kimball, M.L. Lehmann, and J.D. Parker. 2014. Record northernmost endemic mangroves on the United States Atlantic Coast with a note on latitudinal migration. Southeastern Natura list 13:56–63. Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 628 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 Southeastern Naturalist 629 E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 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 Southeastern Naturalist E. McGinley, A. O’Connor, E. Vazquez, and J. Veenstra 2016 Vol. 15, No. 4 630 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