Fish assemblages around oil and gas platforms in the northeastern Gulf of Mexico: developing a survey design

Abstract

Eight platforms of various sizes, configurations, and depths were sampled with a pan and tilt video camera, stationary video cameras, and a remotely operated vehicle (ROV). Differences in fish species observed, and their abundances as measured by the different gear types, were evaluated to determine an optimal sampling design for large-scale surveys. Forty-four taxa from 19 families were observed over all platforms and all gears. More taxa were observed within the confines of the platforms and in close proximity to the platforms than were observed away from the platforms. Camera orientation was important in detecting some species (e.g., grouper were only observed within the confines of the platforms). The number of taxa observed did not vary with depth or among platforms; however, there were differences in fish density with depth and among platforms. More red snapper Lutjanus campechanus were seen at depths grater than 25 m, while more gray snapper Lutjanus griseus were found at depths less than 20 m. Totalfish densities were lower at platforms with barnacles as the dominant attached fauna and higher at platforms with higher relief epifauna (octocorals, sponges, and bryozoans). Red snapper densities were higher at platforms with higher relief epifauna, and gray snapper densities were higher at barnacle-dominated platforms. There was no difference in fish density with platform age nor any relationship between platform age and attached faunal types.