Composition of larval, juvenile, and small adult fishes relative to changes in environmental conditions in Florida Bay

We compared (1) ichthyoplankton composition and (2) basin and channel habit at ichthyofauna and sea grass densities between 1984-1985 and 1994-1996 in Florida Bay. Stations and sampling techniques employed in 1984-1985 were du plicated in the 1994-1996 study. Thalassia testudinum, Halodule wrightii, a nd Syringodium filiforme densities within most of the basin and channel str ata sampled in 1994-1996 had decreased by as much as 100%. We did not obser ve changes in the total density of juvenile and small adult fishes coincide nt with the reductions in seagrass densities except in the deepwater channe l habitats. There was an increase in the proportion of the total ichthyofau na represented by pelagic atherinids, engraulids, and clupeids, particularl y the engraulid Anchoa mitchilli, and a concomitant decrease in the proport ion represented by canopy-dwelling and morebenthic-dwelling seagrass inhabi tants. This suggested a shift toward a planktonic-feeding community. We obs erved an increase in the density and frequency of engraulid larvae, particu larly in the western and Gulf of Mexico portions of Florida Bay, but no sig nificant changes in densities of the commonly collected ichthyoplankton tha t are demersal as adults (i.e., Gobiidae, Callionymidae, and Blennioidei). Lucania parva Eucinostomus spp, Lagodon rhomboides, Floridichthys carpio, H aemulon plumieri, and Syngnathus floridae represented nearly 86% of the juv enile and small adult fish collected in 1984-1985 but represented only 29% of the ichthyofauna a decade later. The distribution of juvenile spotted se atrout had expanded into the central and northeastern basins of our samplin g area, perhaps in response to reduced salinities or to the availability of food resources.