Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

Demographic Differences in Northern Gulf of Mexico Red Snapper Reproductive Maturation: Implications for the Unit Stock Hypothesis

Melissa W. Jackson, James H. Cowan, Jr., and David L. Nieland

doi: https://doi.org/10.47886/9781888569971.ch14

Abstract.—Red snapper, Lutjanus campechanus, has been fished for over a century, with management beginning in the Gulf of Mexico (Gulf) in the early 1990s when perceptions of a declining population size surfaced. Red snapper are managed as a unit stock and the fishery management plan is based upon minimal data regarding reproductive output, and size and age at sexual maturation is not certain. Differences in size and age at sexual maturity of red snapper between the northeast and north-central Gulf were evaluated to test whether the population conforms to the unit stock hypothesis. Red snapper were collected during the spawning season in 1999, 2000, and 2001 from the Gulf off Alabama and Louisiana and were used to describe maturation schedules. Progression of oocyte maturation to vitellogenesis was used to define and identify sexually mature females. Combined data showed the smallest mature red snapper was 267 mm fork length (FL) and was two years old. The smallest with hydrated oocytes, indicative of imminent spawning, or postovulatory follicles, indicative of recent spawning, were 285 mm and 297 mm FL respectively, and both were two years old. Red snapper off Alabama reached maturation at smaller sizes and younger ages than those sampled off Louisiana. Growth rates did not differ between the regions. Such differences in maturation schedules may document an important stock response to reductions in population size.