Relationships Between Reef Characteristics and Reef Fish Community Structure and Demographics in the NE Gulf of Mexico as Revealed in Video and Side Scan Sonar Data

From 2005-2010, the NMFS Panama City Lab has been conducting a stationary video and trap survey of reef fish on hard bottom habitats in the NE Gulf of Mexico. Fish communities, densities, and demographics vary among those habitats, sometimes considerably.  Many sampling sites have been mapped with side scan sonar, providing information on reef type, area, relief, proximity to neighboring reefs, and rugosity.  These variables were quantified and combined into a relative, standardized score for each reef to provide a repeatable, quantifiable measure to use in a weighting scheme when randomly selecting sites for sampling.  Larger reefs with characteristics such as high vertical relief, high rugosity, and close proximity to neighboring reefs received higher rankings.  Data were compared with video, and in some cases trap samples, from each site.  Higher ranking reefs showed greater numbers of species (mean: 10.5 vs. 8.2; p<.01) and higher diversity (mean Shannon Weaver value: 2.5 vs. 1.8; p<.01) than low ranking ones.  Diversity also differed significantly between solid rocky reefs and both scattered and epifauna dominated reefs (p<.01).  Commercially important species such as gag, red grouper, and red snapper also showed increasing numbers on higher scoring reefs.  Black sea bass relative abundance showed a negative relationship with reef score, while white grunt showed no clear patterns.  In general, large rugose reefs with high relief appeared to be higher value reef fish habitat (higher densities and greater diversity), but in some cases, such as black sea bass, the opposite was true.  Such information on habitat associations will be invaluable for increasing precision and accuracy of survey abundance estimates by revealing important strata for both survey design and data analysis.