Declining Size at Age Among Red Snapper in the Northern Gulf of Mexico off Louisiana, USA: Recovery or Collapse?

摘要

The red snapper, Lutjanus campechanus, is currently both overfished and undergoing overfishing in the Gulf of Mexico (GOM) waters adjacent to the southeastern United States. From October 1998 through May 2004, we sampled 6,159 red snapper landed at acommercial dock in Cameron, LA, for morphometrie data and otoliths for age estimation. Despite the species' potential lifespan of more than 50 years, the harvest is almost totally dominated by individuals of ages 2-6 years. Over the course of our sampling we have observed striking, statistically significant decreases in mean total length (TL) at age for red snapper of ages 2—6 years. Density dependence theory tells us that, within a population of fishes that is increasing in numbers, a decrease in resources (food, habitat, etc.) per individual might be manifested in a compensatory decrease in growth rate. Thus, the declines in red snapper mean TL at age may be an expression of recovery of an overfished population. Conversely, the heavy commercial andrecreational harvest of young red snapper in the northern GOM, many of them at the very minimum TL required for retention, may have resulted in an inadvertent selection for the survival of slow-growing individuals.