The webbing reef: a tool used in the study of juvenile red snapper (Lutjanus campechanus)

Abstract

The primary purpose for requiring shrimp trawlers to use bycatch reduction gear in the U.S. Gulf of Mexico is to reduce the incidental capture and mortality of juvenile red snapper (Lutjanus campechanus). Developing effective bycatch reduction devices (BRDs) for this purpose requires a good understanding of juvenile snapper behavior and their reaction to different trawl components, which is being accomplished through diver observations on shrimp trawls and with trawl attached cameras. Early BRD development was dependent on chance encounters with juvenile snapper, but that changed in the mid-1990s with the invention of the trawlable webbing reef. The webbing reef proved to be ideally suited for attracting and concentrating juvenile red snapper for BRD studies, and its design was perfected to the point that it is now a simple, easily deployed, self-anchoring system. From habitat studies, we learned that we could selectively attract either age-0 or age-1 snapper by adjusting reef height and applied this in the design of the latest webbing reef. In the process of studying BRD escapement and site fidelity, we determined that juvenile red snapper have homing capabilities. Young snapper were observed residing at a webbing reef for almost four months, and displaced snapper were able to return to their original habitat from a distance of almost 2 km. Our study on spatial and temporal recruitment patterns indicates greater recruitment and longer residence time on reefs off Mississippi than off Alabama or Florida. A major factor affecting recruitment off Mississippi in 2001 was the occurrence of hypoxia which caused the loss of all red snapper and most of the invertebrates on and around the reefs. While the webbing reef has been an invaluable tool for increasing our knowledge of juvenile red snapper, its use is not limited to snapper studies. The webbing reef attracts and provides habitat for other species of fish, invertebrates and plants and, because of its simplicity and portability, can be used for long or short term projects in almost any marine environment.