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

Population Dynamics and Structure Overview

David L. Nieland

doi: https://doi.org/10.47886/9781888569971.ch9

Over the past two decades we have learned much about red snapper Lutjanus campechanus biology, life history, and ecology, all of which has improved our understanding of the red snapper in the Gulf of Mexico (GOM) both as a species and as a resource. We have also applied new technologies and new techniques to our research efforts that have allowed us to look at red snapper populations at much finer scales of differentiation. Section II of this book is composed of seven papers addressing population dynamics and population structure of red snapper in the U.S. GOM. Together they illustrate the changing approaches to our study of red snapper populations and the wide variety of techniques, from traditional to molecular to mathematical, employed in our collective research on the species; individually they provide information vital to our understanding both of red snapper populations and of the strategies that might be appropriately applied to red snapper management.

The first two papers by Andrew Strelcheck et al. and Sandra Diamond et al. examine the site fidelity and movements of tagged/recaptured red snapper, the former at low relief artificial reefs off the coast of Alabama and the latter at both natural reefs and artificial reefs (mostly petroleum platforms) off the Texas coast. The moderate site fidelity and the comparatively low vagility reported in both studies suggest that local populations of red snapper in the GOM may be relatively isolated from one another and may warrant management on a more regional, rather than Gulf-wide, basis. Strelcheck et al. further state that the artificial reefs off Alabama are suitable habitat for adult red snapper, yet they support a net loss of biomass due to high fishing mortality.

The third paper is Andrew Fischer’s synopsis of the evolution of fisheries ageing and validation techniques as they have been applied to red snapper in the GOM. He begins with early efforts to age red snapper from scale annuli and continues through to the current practice of counting annuli in sectioned otoliths. The increase in potential longevity of red snapper, from less than 10 years to almost 60 years, realized over the span of the studies discussed may have impacted red snapper management as much, or more, than any other life history datum. Fischer also includes sections addressing ageing precision and accuracy and the application of (and pitfalls of) the von Bertalanffy growth model to red snapper length at age data.

John Gold and Eric Saillant contribute the fourth paper of this section, a study of the population structure of red snapper based on analyses of allelic variation in nuclear- encoded microsatellites and of haplotype variation in mtDNA. They conclude that red snapper in the GOM maintain a complex of semiisolated populations in which relatedness is maintained over geologic time by gene fl ow, yet the populations are demographically independent over the short term. This would appear not only to support the limited movement of red snapper reported by Strelcheck et al. and Diamond et al., but also to argue for regional management of red snapper populations in the GOM.