Benthic Habitats, as Derived from Classification of Side-Scan-Sonar Mapping Data, Are Important Determinants of Reef-Fish Assemblage Structure in the Eastern Gulf of Mexico

Abstract

Increasingly restrictive management regulations have greatly reduced the utility of fishery-dependent data for characterizing temporal changes in the abundance of managed fish populations, so fishery-independent data are becoming more important for the accurate assessment of stock status. A notable downside to fishery-independent data is the high cost of conducting surveys, and efforts to maximize survey efficiency are critical given ongoing reductions in agency funding. We conducted a pilot study to explore the utility of classifying side-scan-sonar mapping data to provide a practical a priori characterization of reef habitat in the eastern Gulf of Mexico. An analysis of side-scan-sonar mapping data identified five distinct reef habitat types (low-relief hard bottom, mixed hard bottom, fragmented hard bottom, ledges, and potholes) that were subsequently sampled with stereo baited remote underwater video (S-BRUV) arrays and trap-mounted GoPro cameras. The permutational analysis of variance indicated that the assemblage structure of reef fish differed significantly (P < 0.01) among all of the pairs of habitats except ledges and fragmented hard bottom; assemblage structure did not differ among cameras (P = 0.45). Overall species richness and diversity were significantly higher in the habitats with greater vertical relief, as were the abundances of several economically and ecologically important reef fishes, although many taxa were observed across all of the habitat types. Benthic habitats that are identified from side-scan-sonar mapping data are important determinants of reef-fish assemblage structure and may prove to be useful as a stratification scheme for reef-fish surveys, although additional research is necessary to explore the transferability of these results to the rest of the eastern Gulf of Mexico.