Fidelity of red snapper (Lutjanus campechanus) to petroleum platforms and artificial reefs in the northern Gulf of Mexico

Abstract

The habitat value of petroleum platforms for red snapper, Lutjanus campechanus, is poorly understood. However, it is widely recognized by both scientists and fishermen that the presence of platforms in the northern Gulf of Mexico (GOM) has affected the distribution of red snapper by the addition of hard substrate habitat. We evaluated the habitat value of standing and toppled platforms by monitoring the fidelity of red snapper to these structures with acoustic telemetry. In May 2003, 125 red snapper were captured with hook and line at several platforms in a 35-km² portion of the South Timbalier oil and gas lease blocks, 50 km south of Port Fourchon, LA. Following anaesthetization with MS-222, an individually coded acoustic pinger was surgically implanted into the peritoneal cavity of each fish. After a short recovery period the red snapper were released at five platforms in the study area. Presences of individual snapper were recorded with omnidirectional acoustic receivers attached to seven platforms, and to one artificial reef, a toppled platform. Red snapper exhibited little movement between platforms in the study area. However, logistic regression showed a high initial fidelity to release location which subsequently decreased over time, thus site fidelity was found to be high in the short-term, but much lower in the long-term. This result differs from previous studies on red snapper fidelity that reported high fidelity over longer time spans. Red snapper recaptured outside of the study area showed little uniform directional movement. Estimates of instantaneous fishing mortality on this population were higher than those predicted by the most recent stock assessment. A Fourier analysis revealed a diel pattern of movement away from the structures at night, most likely for offsite foraging. Knowledge of red snapper fidelity to petroleum platforms will lead to more effective management of this species by clarifying both the specific function of these structures as habitat and their importance to the red snapper population in the GOM.