NEARSHORE HABITAT USE BY GRAY SNAPPER (LUTJANUS GRISEUS) AND BLUESTRIPED GRUNT (HAEMULON SCIURUS): ENVIRONMENTAL GRADIENTS AND ONTOGENETIC SHIFTS

摘要

Fringing mangrove forests and seagrass beds harbor high densities of juvenile snappers and grunts compared to bare substrates, but their occupancy of these habitats is not homogeneous at ecologically meaningful scales, thus limiting our ability to compare habitat value. Here, density and size information were used to determine how gray snapper, Lutjanus griseus (Linnaeus, 1758) and bluestriped grunt, Haemulon sciurus (Shaw, 1803), use vegetated habitats during their ontogeny, and how their use of mangrove forests varied with season across broad spatial scales and physicochemical conditions. Both species exhibited a three-stage ontogenetic strategy: (1) settlement and grow-out (8-10 mo) within seagrass beds, (2) expansion to mangrove habitats at 10-12 cm total length, and (3) increasing utilization of inland mangroves during the dry season and with increasing body size. For fishes inhabiting mangroves, multivariate tests revealed that the factors distance from oceanic inlet and water depth were stronger predictors of reef fish utilization than the factors latitude, temperature, or habitat width. These findings highlight that the nursery function of mangrove shorelines is likely limited to the area of immediately accessible habitat, and that more expansive forests may contain a substantial number of larger adult individuals.