The Relationship of Seagrass-Associated Fish and Crustacean Communities to
Habitat Gradients in Florida Bay
R.E. Matheson and David Camp
FWC, Florida Marine Research Institute, St. Petersburg, FL
Mike Robblee
USGS, Center for Water and Restoration Studies, Miami, FL
Gordon Thayer and Dave Meyer
NOAA, NCCOS, Center for Coastal Fisheries and Habitat Research, Beaufort,
NC
Lawrence Rozas
NOAA Fisheries, Estuarine Habitats and Coastal Fisheries Center, Lafayette, LA
Restoration of the greater Everglades ecosystem will be multifaceted, but a large
component of the program involves reestablishing a more natural hydrological
regime. Downstream of the Everglades, changes in the quantity, timing, and
distribution of freshwater flows entering Florida Bay will affect the resident biota.
This project was designed to provide baseline data for one important faunal
component of the Florida Bay ecosystem: seagrass-associated fish, caridean and
penaeid shrimp, and portunid crabs. Seagrass beds are one of the most spatially
extensive and important habitats in Florida Bay, and the extent, composition, and
health of seagrass beds can definitely be affected by changes in freshwater inflow.
Seagrass-associated faunal communities can be affected directly by salinity
changes or indirectly by changes in the seagrass habitat. This study provides
baseline data needed by managers to create models that can predict what will
happen as a result of changes in freshwater delivery to Florida Bay and to
evaluate the success of upstream restoration activities.
We used 1-m2 throw-traps to collect seagrass-associated fauna at 18 sites
distributed throughout Florida Bay. For analytical purposes, our sites can be
grouped geographically (Fig. 1): 1) northeast—Black Betsy, Bob, Butternut, Deer,
Eagle, and Nest Keys; 2) interior—Bob Allen, Buttonwood, Crab, Roscoe, Spy,
and Whipray Keys; and 3) peripheral—Barnes, Joe Kemp, Johnson, Palm, Rabbit,
and Sandy Keys. Three habitats (bank, basin, and near-key) were sampled at each
site during wet (October) and dry seasons (April-May) from 1998 through 2000,
yielding 360 bank samples, 360 basin samples, and 270 near-key samples. We
identified 7,539 fish and 62,786 shrimp and crabs from these samples.
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A gradient was apparent in both habitat features and biotic communities across
the three regions (Table 1). Northeastern sites had lower, more variable salinities;
shallower sediments; less seagrass cover; and lower diversity and abundance of
fish and crustaceans. Levels of these same parameters were often intermediate at
interior sites and highest at peripheral sites.
The abundance patterns of the five dominant fish species were less consistent with
this gradient than were the abundance patterns of the five dominant crustacean
species. The abundance of only one fish species, Lucania parva, strictly followed
the gradient of northeast<interior<periphery, and two fish species, Floridichthys
carpio and Opsanus beta, were found at similar abundances in all three regions.
Anchoa mitchilli and the sixth-ranked species, Microgobius gulosus, were both
most abundant at northeastern and interior sites; both of these species are often
found in the low-salinity portions of estuaries and are weakly associated (if at all)
with seagrass. Among crustaceans, abundances of the top five species were all
low in the northeast, moderate or high in the interior, and high on the Bay’s
periphery. The strongest apparent relationships between abundance and salinity
were observed for Farfantepenaeus duorarum and Gobiosoma robustum. Both of
these species were essentially absent at salinities below 29 ppt but were among
the most abundant species at higher salinities. Greater seagrass-bed development
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(i.e., greater density, leaf area, or diversity) was often accompanied by greater
abundances of several species, including F. duorarum, G. robustum, Thor
floridanus, and O. beta.
Table 1. Characterization of habitats and faunal communities in three regions
within Florida Bay. Seagrass diversity is determined by the relative
contribution of each of the species collected during this study to the overall
abundance of seagrass in each region. Only the five most abundant fish and
five most abundant crustacean species are included.
Parameter
Northeast
Interior
Periphery
Salinity
low
high
high
Salinity CV
high
low
low
Sediment Depth
low
moderate
high
Seagrass Shoots
low
moderate
high
Seagrass Biomass
low
moderate
high
Seagrass Diversity
low
moderate
high
Seagrass Canopy Height
low
moderate
high
Fish Abundance
low
moderate
high
Number of Fish Species
low
low
high
Lucania parva
low
moderate
high
Gobiosoma robustum
low
high
moderate
Floridichthys carpio
moderate
moderate
moderate
Opsanus beta
moderate
moderate
moderate
Anchoa mitchilli
high
high
low
Crustacean Abundance
low
moderate
high
Number of Crustacean Species
low
moderate
high
Thor floridanus
low
high
high
Hippolyte zostericola
low
moderate
high
Farfantepenaeus duorarum
low
moderate
high
Alpheus heterochaelis
low
high
high
Periclimenes americanus
low
moderate
high
Alterations in the pattern of freshwater inflow could affect most of the physical
and biotic patterns which we observed in Florida Bay. The effects of these
alterations on fauna will be species-specific. Our study provides data for
predicting these changes prior to restoration and for documenting these changes
after restoration.
R.E. Matheson, Florida Fish and Wildlife Conservation Commission, Florida
Marine Research Institute, 100 8th Avenue SE, St. Petersburg, FL 33701, Phone:
(727)896-8626, Fax: (727)8230166, eddie.matheson@fwc.state.fl.us, Question 5
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