Red snapper recruitment to and disappearance from oil and gas platforms in the northern Gulf of Mexico

Abstract

The red snapper Lutjanus campechanus is a potentially large and long-lived species which can
achieve ages approaching 60 years and weights of over 22 kg. In the northern Gulf of Mexico, oil
and gas platforms provide the preponderance of both vertical relief and hard substrate habitat for red
snapper and other reef associated fishes. In July 1998, we collected morphometric data and sagittal
otoliths from 300 red snapper randomly selected from among the mortalities manifested subsequent
to the explosive removal of an obsolete gas platform. Ages estimated from counts of otolith annuli
ranged from one to nine years among these specimens. The virtual absence of age-one red snapper
(0.68%) and the preponderance of age-two red snapper (53%) at the platform demonstrates that red
snapper recruit to platforms sometime during their second year. Truncation of the age distribution
results from natural mortality, fishing mortality, and emigration to other habitats after several years
of residency. Assuming this population to be typical, the age distributions of the commercial and
recreational harvests suggest that oil and gas platforms serve as essential habitats for younger red
snapper. Conversely, platforms may make red snapper at ages four, five, and six year more
vulnerable to fishing mortality as they are perhaps being harvested in proportions greater than their
numbers in the population at large.