Community structure and environmental drivers of offshore hard-bottom reef fishes in the northern Gulf of Mexico

Abstract Understanding patterns in community structure in large marine ecosystems is necessary for advancing community- and ecosystem-based approaches to marine fisheries management. We analyzed data from a large-scale, fishery-independent video survey to quantify the structure of reef fish communities on offshore hard-bottom reef habitats in the northern Gulf of Mexico (nGOM). A novel aspect of this work is that all species visualized on videos were identified and enumerated over a 13-year period, which allowed for a comprehensive analysis of fish community structure. We observed a total of 243 fish species from 54 families and 14 orders. Species richness and biodiversity varied considerably across the nGOM and were highest in regions that harbor extensive coral reef habitat (south Florida, Louisiana-Texas shelf). Multivariate analyses identified 12 species assemblages, with important fishery species and species of concern (i.e. IUCN-listed) occurring in the largest identified assemblages. One assemblage composed mostly of large-bodied fishery species accounted for 45% by number and 89% by weight of all fish observed. Species assemblages were most strongly associated with depth, temperature, and substrate composition, with weaker associations with the amount of attached algae and vertical relief, while species richness was positively correlated with bottom water temperature. In general, large-scale bathymetric and hydrographic factors (e.g. depth, temperature) were more important than local topographic structure and biogenic habitat in structuring reef fish communities at the spatial scales (i.e.1000 km) considered here. Our results advance ecosystem-based approaches to fisheries management by providing a basis for incorporating multispecies spatial dynamics into the monitoring and assessment of hard-bottom reef fish communities in the nGOM.