Abstract

There has been much debate about how structure, such as natural and artificial reefs, affects the community of reef-associated fishes at the process-level. Studies have shown fishes select habitat based upon needs for refuge from predators, substrate for spawning, or feeding, and, by extension, prey availability. Direct comparisons of trophic diversity among habitat types can be difficult owing to gear inefficiencies, which is particularly true for complex reef habitats. We used stable isotopes, specifically the ?13C ?15N biplot, as a method to determine trophic niche breadth in three species of fishes in the northern Gulf of Mexico with contrasting life histories that occupy different habitats. We compared the feeding ecology of red snapper (Lutjanus campechanus) among habitat types (reef, sand, and shell), age groups (0, 0.5, 1, 2, and 3+), and trawled and non-trawled habitat. Results were contrasted with those of spotted seatrout (Cynoscion nebulosus), and Atlantic croaker (Micropogonias undulatus) feeding over an inshore artificial oyster reef and a mud-bottom habitat. Results indicate differences in niche breadth among habitats for both spotted seatrout and Atlantic croaker, and due to trawling and ontogeny for red snapper. Red snapper niche breadth was greater in trawled habitats as compared to non-trawled for all habitat types. Results also suggest age-0 red snapper have a relatively small trophic niche, which expands for older juveniles (age-0.5) and sub-adults (age-1), and then contracts as fish enter adulthood (ages 2 and 3+). Investigation of trophic niche breadth may be a promising technique to elucidate feeding patterns across species.

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