Abstract

We examined the community, size, and trophic structure of reef fishes at 61 reef sites in the northern Gulf of Mexico as part of an ongoing study to examine ecological differences between artificial and natural reefs. There were significant differences in fish community structure between reef types and depths (ANOSIM; p < 0.001), with large piscivores being more abundant at artificial reefs while planktivores and invertivores were more abundant at natural reef sites. Species diversity was greater at natural sites, which was mostly due to the myriad small fishes present there but not on artificial reefs. Overall, fish density was an order of magnitude greater at artificial reefs, although natural reefs covered more expansive areas. There was a significant difference in fish size between reef types (ANOVA; p < 0.001), with some fishery species, such as red snapper, gray triggerfish, and greater amberjack, being larger at artificial reefs, and others, such as vermillion snapper, scamp, and red porgy, being larger at natural reefs. Too few stomach samples were available for most species to test diet differences between natural and artificial reefs, with an exception being red snapper (n = 336). Red snapper displayed a clear ontogenetic shift in feeding at higher trophic levels with increasing size, but fish in natural habitats also displayed broader diets than fish on artificial reefs. Ongoing stable isotope analysis (CNS) of muscle samples (n = 308 samples among 33 species) should provide greater resolution of trophic structure of reef fish trophic structure.

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