A Comparison of Size Structure, Age, and Growth of Red Snapper from Artificial and Natural Habitats in the Western Gulf of Mexico

Abstract

Red Snapper Lutjanus campechanus support economically important fisheries in the Gulf of Mexico (GOM) and have been classified as overfished since the first stock assessment was conducted in 1988. Although the stock is now showing signs of recovery, management could benefit from a better understanding of regional or even habitat-level differences in stock demographics, as these dynamics ultimately determine overall stock productivity. From 2012 to 2014, we used a fishery-independent vertical line survey to assess Red Snapper relative abundance, size and age structure, and growth parameters at standing oil and gas platforms, decommissioned platform artificial reefs, and natural banks in the western GOM. We captured 1,170 Red Snapper ranging from 275 to 855 mm TL. Vertical line CPUE data showed no differences among the three habitat types. Ages determined for 1,143 individuals ranged from 2 to 30 years; however, most (90%) were younger than age 8. Size and age frequencies revealed that natural banks supported a greater proportion of large and relatively old fish compared to standing platforms or artificial reefs, although this difference was heavily influenced by a single bank that had significantly larger and older Red Snapper than other sites. Mean age was not significantly different among habitat types. Among a suite of growth models fitted to size-at-age data, the logistic model provided the best fit and suggested that fish from artificial reefs reached larger sizes at age than fish from either standing platforms or natural banks. Our study provides the first estimates of habitat-specific growth parameters for Red Snapper in the western GOM, and this information can benefit future stock assessments. This study also highlights the potential benefits of artificial reefs to Red Snapper and indicates that all habitats could contribute similarly to stock productivity on a per-unit-area basis.

Received December 21, 2016; accepted March 14, 2017 Published online May 26, 2017

ACKNOWLEDGMENTS

We thank the staff, students, and interns of the Center for Sportfish Science and Conservation for their help in sampling and processing Red Snapper. Staff at the Harte Research Institute for Gulf of Mexico Studies also contributed essential logistic support. We are grateful to the two anonymous reviewers, who provided constructive comments that significantly improved the manuscript. Funding for this research was provided by the TPWD Artificial Reef Program through interagency contract numbers 415254, 439195, and 474362. Further funding for this work was provided by the Marine Fisheries Initiative Program (Grant Number NA14NMF4330219).