Fish assemblages around oil and gas platforms in the northeastern Gulf of Mexico: developing a survey design
Abstract
A pilot survey was conducted in 1995 by the National Marine Fisheries Service, Mississippi
Laboratories (NMFS, ML) to develop a survey design for assessing fishes associated with the
offshore oil and gas platforms in the Gulf of Mexico (GOM). 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 abundance
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. The ten most
frequently observed species were: blue runner, Caranx crysos; Atlantic spadefish, Chaetodipterus
faber; gray (mangrove) snapper, Lutjanus griseus; sheepshead, Archosargus probatocephalus; red
snapper, Lutjanus campechanus; great barracuda, Sphyraena barracuda; lookdown, Selene vomer;
the scad complex, Decapterus spp. and/or Trachurus sp.; gray triggerfish, Balistes capriscus; and
blue angelfish, Holacanthus bermudensis. 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., groupers were only observed
within the confines of the platforms. The number of taxa observed did not vary with depth or among
platforms, but there were differences in fish density with depth and among platforms. More red
snappers were seen at depths > 25 m, while more gray snappers were found at depths < 20 m. Total
fish 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 observed in fish density with platform age
nor any relationship between platform age and attached faunal types.