Estuaries are vital nursery grounds for many marine fishes. During initial estuarine residence, juvenile fishes presumably benefit greatly from rapid growth, which can diminish susceptibility to size-selective predators. To measure the degree of variability in growth rates across different estuarine sites and habitats. I conducted caging experiments with 3 species (Pseudopleuronectes americanus, Tautoga onitis, and Gobiosoma bosci) at 4 sites in New Jersey, USA, estuaries. Two sites were in an estuary with dense eelgrass Zostera marina beds (Little Egg Harbor) and 2 were in an estuary lacking eelgrass but supporting patchy accumulations of the macroalgae Ulva lactuca (Great Bay).Experiments were conducted in vegetated (either Zostera or Ulva) and unvegetated habitats at each site. Relative differences in growth rates among the 4 sites and between the 2 habitats were generally maintained across experiments withln species, suggesting a consistency in foraging value. For all 3 species, growth .was highest at a Great Bay site and generally lowest at a httle Egg Harbor site. The presence of vegetation (either Zostera or Ulva) was beneficial to growth only for T onitis. Observed patterns in water temperature, sediment structure, and food availability were potential factors effecting the observed differences in growth rates. Natural densities of the 3 fish species were quantified and compared to the results of growth experiments to determine if there were trade-offs between rapid growth and other attributes of habitat quality. P. americanus and T onitis were more abundant in areas supporting faster growth, but the complete absence of tautog from unvegetated substrates suggested some degree of habitat avoidance. A clear trade-off between habitat selection and foraging quality occurred for G. bosci; gobies were most abundant inside eelgrass beds, which supported the poorest growth rates.

ABSTRACT. Epibenthic fish comn~unities residing in seagrass beds on shallow (<0.5 m) mudbanks in Florida Bay. USA, were quantitatively sampled with a throw trap method. 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 is proposed to be a 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 are proposed as constraints on larval avdability. 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 in&vidual 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.