Selective use of mangrove shorelines by snappers, grunts, and great barracuda

We examined seasonal utilization of >500 km of mangrove shoreline within a subtropical continental system by Lutjanus griseus, L. apodus, Haemulon sciurus, H. parra, and Sphyraena barracuda over 2 consecutive years. Mangrove use by these species was examined in terms of frequency of occurrence, density (fish 60 m(-2)), Concentration (density among samples where number of fish >= 1), and selection (H-0: habitat use = availability). All species exhibited either seasonal or spatial habitat selection. Mangrove shorelines closest to the reef tract (Keys) were used by snappers and grunts at much greater levels than their availability would suggest, whereas more inland and expansive mangrove shorelines were largely selected against. This selection pattern was evident year round for L. apodus, H sciurus, and H. parra. In contrast, L. griseus preferred more inland mangroves during the dry season and Keys mangroves during the wet seasons. S. barracuda exhibited selection for Keys during the wet seasons and was the only species to exhibit non-selection (random) patterns among strata during the dry seasons. These results demonstrate that mangrove shorelines across broad spatial scales are not equivalent in their value as fish habitats, and that estimates of 'essential fish habitat' or 'nursery habitat' using total habitat area will grossly overestimate the amount of functional habitat used by these reef fishes.