Effect of reef morphology and depth on fish community and trophic structure in the northcentral Gulf of Mexico
Reef fish resources provide numerous ecosystem services in the northern Gulf of Mexico (nGOM) large marine ecosystem. Artificial reefs (ARs) have been distributed across the nGOM in attempts to enhance reef fish habitat and increase fishery productivity, but few data exist to distinguish ecological from fishery functions of ARs compared to natural reefs (NRs), particularly at the regional scale. Therefore, we conducted remotely operated vehicle surveys of reef fish communities at 47 reef sites within a ∼20,000 km2 area of the nGOM shelf and tested the effect of reef type (NR versus AR), depth (≤35 or >35 m), relief (≤2 m or >2 m), and complexity (low or high) on fish diversity and community structure as well as trophic guild- and species-specific densities. Twenty-one species were present at >20%, nine at >50%, and three at >75% of study reefs. Fishery species (i.e., Lutjanus campechanus, Seriola dumerili, and Rhomboplites aurorubens) and invasive Pterois volitans were frequently observed (>50% of sites) or numerically dominant, especially at ARs. Main effects did not significantly affect the presence of specific species or trophic guilds, but interactions among factors significantly affected species- and trophic guild-specific densities. Our results indicate that effects of habitat characteristics on fish communities are more nuanced than previously described. Fish communities are moderately similar at the majority of sites but specific habitat characteristics can interact to dramatically affect densities of some species, particularly those that depend on complex structures for refuge. Simple ARs tend to concentrate high densities of a few important fishery species with low densities of other small demersal reef fishes. Complex NRs with high relief also support high densities of planktivorous fishery species but greatly increase densities of small, demersal, non-fishery species that directly utilize complex reef structure for refuge.