Habitat Selection Important for Red Snapper Feeding Ecology in the Northwestern Gulf of Mexico

Abstract

The present study compared Red Snapper Lutjanus campechanus feeding ecology among seasons, sizes, and natural reefs, and between natural and artificial reefs located on the Louisiana shelf edge. As low-quality diets may hinder growth, reduce condition, and lead to poor reproductive output, information on diets for various habitat types occupied by Red Snapper is critical. This study utilized both stomach content analysis and nitrogen (δ¹⁵N) and carbon (δ¹³C) stable isotope analysis of muscle tissue. Fishes dominated Red Snapper diets at all sites, in all seasons, and generally for all size-classes. A high biomass of zooplankton was consumed at the artificial reef area and during spring. The largest natural reef provided the widest diversity of prey items, and there was little overlap in prey species consumed between natural and artificial reef habitats. Higher δ¹⁵N and lower δ¹³C values were found for Red Snapper at the artificial reef area, and contrary to the diet results, distinct isotopic niches were found between natural reefs. Differences in Red Snapper isotopic niches between natural reefs indicate that individuals may remain in residence on a specific reef for an extended period. Red Snapper at natural reefs were found to feed on and above the reef, whereas feeding at artificial reefs predominantly occurred on the surrounding seafloor and up in the water column. The quality of habitats underlying reefs is important, as Red Snapper diets reflected the substrate at the occupied reefs. In the northwestern Gulf of Mexico, large, complex natural reefs may provide higher habitat quality for Red Snapper with respect to prey resources than artificial reefs located on mud substrates. Determining which habitats provide high-quality prey resources for Red Snapper in the Gulf of Mexico may assist decisions on policies and regulations for habitat protection as well as decisions on the future placement of artificial reefs.

Received March 8, 2017; accepted June 13, 2017

ACKNOWLEDGMENTS

This project was funded by the Louisiana Department of Wildlife and Fisheries (Grant 169-52-4105). Work was conducted under National Marine Fisheries Service Letter of Acknowledgement Number F/SER24 and was approved by the Institutional Animal Care and Use Committee at Louisiana State University (Protocol Number 10-032). We thank the captain and crew of the M/V Blazing 7, as well as Hilary Glenn, Marshall Kormanec, Jackie McCool, Dave Nieland, and the other volunteers for their help with field collections. We are grateful to Joey Heintz and Shanna Lambert for help with stable isotope preparation; Brian Marx and Jill Olin for assistance with stable isotope statistical analyses and interpretation; Darryl Felder for help in identifying the crustacean prey items; and two anonymous reviewers for providing thoughtful and helpful comments that improved the manuscript.