Documenting deepwater habitat utilization by fishes and invertebrates associated with Lophelia pertusa on a petroleum platform on the outer continental shelf of the Gulf of Mexico using a remotely operated vehicle

Marine communities associated with oil and gas platforms beyond the continental shelf are poorly described islands of potential interaction between structure oriented and pelagic taxa. Near-bottom, biological surveys were conducted at a petroleum platform located in 305 m water depth off the coast of Louisiana between 268 m and the seabed. Surveys were performed with a remotely operated vehicle (ROV) and consisted of replicated benthic transects on all four sides of the platform extending 125 m outward from the platform. The fouling community on hard surfaces of the horizontal cross-members and verticals were surveyed using HD video and digital still images. Relative abundances of fishes were estimated using digital still images collected at regular intervals under three illumination regimes: no light, red light, and white light, while the ROV hydraulics were switched off to reduce vehicle noise. Additional surveys of fishes were conducted during day and night at the platform and at two far-field sites located 2 km and 3 km from the platform by monitoring species attracted to buckets containing an olfactory attractant. The results indicated abundant coldwater coral Lophelia pertusa present on the platform and on the surrounding rubble near the platform. The fish assemblage at the platform was dominated by American barrelfish Hyperoglyphe perciformis, greater amberjack Seriola dumerili, Darwin's slimeheads Gephyroberyx darwinii, snowy grouper Epinephelus niveatus, misty grouper Hyporthodus mystacinus, American conger Conger oceanicus and Scorpaenidae. The fish community at the farfield site was substantially different and less diverse than that observed at the platform and was dominated by king snake eels (Ophichthys rex) and Scorpaenidae. The results indicate that multiple methods and both day and night surveys are necessary to obtain a more complete picture of the biological community around platforms located on the outer continental shelf. The use of red-filtered lights and quiet surveys without hydraulic pumps on can further reduce avoidance artifacts.