Abstract

Red snapper, Lutjanus campechanus, were sampled in 2009-10 at northern Gulf of Mexico (GOM) natural (n = 10) and artificial (n = 9) reef sites to test for the effect of fish size and habitat type on diet and trophic position. Stomachs (n = 231) were sampled for diet analysis and white muscle tissue (n = 49) was sampled for stable isotope analysis (?13C, ?15N, and ?34S). Forty-four percent of stomachs (n = 104) had identifiable prey, with 56 of those fish sampled at natural reefs and 48 sampled at artificial reefs. Zooplankton (38%), fish (35%), and decapods (17%) constituted most of the observed diet. Habitat type did not affect diet (PERMANOVA, p = 0.087), but fish size was significant (PERMANOVA, p = 0.023). An ontogenetic shift was apparent among red snapper size classes in that smaller fish preyed most heavily on other fishes and decapods, while larger red snapper had a higher percentage of zooplankton in their diet. That finding was corroborated by significantly higher ?15N values for red snapper <400 mm total length (TL) relative to fish 400 - 500 mm or > 500 mm TL. Habitat type was not significant for ?15N (ANOVA, p = 0.777), and neither fish size nor habitat were significant for ?13C or ?34S (p ? 0.340). Overall, data from this study indicate red snapper have a broad diet and are capable of feeding across multiple trophic levels, and that there is little evidence for differences in red snapper diet or feeding ecology between artificial and natural reefs. The occurrence of the Deepwater Horizon Oil Spill (DHOS) in summer 2010 greatly affected the original design of this study, but data collected provide an important pre-spill reference for red snapper diet and trophic ecology in the northern GOM.

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