Epibenthic fish communities residing in seagrass beds on shallow (< 0.5 m) mudbanks in 
Florida Bay were quantitatively sampled with a throw trap method. Sampling took place 
three times a year during 1984 to 1985. The overall average density of 11 fish m 2 
was substantially higher than most previously reported densities for seagrass habitats. 
Four sites, representing 4 different subenvironments of Florida Bay, differed widely in 
species composition and densities of individual species. Results of discriminant function 
analysis indicated that fish communities at the 4 sites were relatively distinct. Species 
composition at different sites may be the result of complex interactions between the 
deterministic influence of habitat quality and the stochastic influence of larval 
availability. Restricted water circulation, effected by the network of banks, and 
different sources of water mass exchange were proposed as constraints on larval 
availability. Differences in species richness and fish densities across individual banks 
corresponded to gradients in depth, sediment structure, detrital loads, and various 
measures of seagrass structural complexity. The greater physical stress on top of a 
bank appeared to limit species richness, while fish densities across individual banks 
were regulated by habitat gradients. Multiple regression analysis indicated that the 
standing crop of seagrasses and the accumulation of vegetation litter were important 
determinants of fish densities. Physical factors, such as depth and sediment structure, 
were also influential. 
1984 - 1985 
Sogard, S. M., G. V. N. Powell, and J. G. Holmquist (1989) Spatial distribution and trends in 
abundance of fishes residing in seagrass meadows on Florida Bay mudbanks. Symp. on 
Florida Bay: A Subtropical Lagoon. Miami, FL. June, 1987. Bull. Mar. Sci. . 44(1 ):179-99. 
Fishes inhabiting seagrass beds on shallow mudbanks in Florida Bay were sampled with 
throw traps, to capture the relatively sedentary, epibenthic species, and gillnets, to 
capture the more mobile species occupying the overlying water column. There was a 
strong heterogeneity in species composition and abundances of both components across 
different subenvironments of the Bay. The Interior section, characterized by a low tidal 
range and hypersaline conditions, harbored few epibenthic species relative to sites on 
the periphery of the Bay. Densities of Lucania parva. however, reached outstanding 
values, with a mean of 39 fish per m 2 at a West Interior site. Species richness of the 
water column component was also low in the Interior subenvironment, but a few 
species had high capture rates, despite salinities of up to 50 °/oo. Three years of 
sampling in the northeast subenvironment indicated a trend from estuarine to marine 
conditions in salinity regime, seagrass growth, and densities of epibenthic fishes. A 
conceptual model was developed to aid in understanding the potential role of various 
biotic and abiotic factors in structuring fish communities on the banks. The 
distinctiveness of different subenvironments suggests that physical factors of water 
circulation and salinity patterns play a more influential role in Florida Bay than in more 
congruous seagrass ecosystems. This paper described the 1984 and 1985 results of the 
study. The results from the first two years of the study can be found in Sogard et al. 
(1987) and Sogard et al. (1989). 
1984 - 1985 
Thayer, G. W., D. R. Colby and W. F. Hettler (1987) Utilization of the red mangrove prop 
root habitat by fishes in south Florida. Mar. Ecol. Proa. Ser. . 35:25-38. 
The inherent difficulty of sampling the red mangrove prop root habitat has impeded our 
understanding of the utilization of this habitat by fishes. A block net and rotenone 
method was developed and used to sample 2 sites in each of 4 regions in Everglades 
National Park. At each site a 3-mm mesh net was used to enclose 3 sides of a mangrove 
island while an onshore berm formed the fourth side. Samples collected from the 
mangrove prop root environment were compared with samples collected using a 2-boat 
290 
