Benthic Habitats and the Effects of Fishing

Symposium Abstract: Linking Predator and Prey Species Dynamics in Deep-Water Reefs of the Northeastern Gulf of Mexico

P. E. Thurman, G. Dennis, K. Sulak, and R. S. McBride


Deep-water reefs common to the Gulf of Mexico provide essential habitat for economically important species such as red snapper (Lutjanus campechanus), grouper (Epinephelus/Mycteroperca spp.), and amberjack (Seriola spp.). Recent diet studies of these predators indicate small serranids (<150mm SL) such as roughtongue bass (Pronotogrammus martinicensis) and red barbier (Hemanthias vivanus) are an important link between zooplankton and these predators. Life history data and video population estimates are being analyzed to determine if these predators affect the size and age structure, distribution, and abundance of these prey species. Ages of 182 P. martinicensis and 80 H. vivanus were estimated by examining the ring structure on whole sagittal otoliths. Although we cannot validate the periodicity of ring formation until year-round samples have been examined, most of the fish collected during May had a ring that was either newly formed or on the margin. Individuals of both prey species grew rapidly through their first year and then growth slowed significantly. Modal ages of P. martinicensis and H. vivanus were 3 and 4 years, respectively. The oldest P. martinicensis examined was 8 years and the oldest H. vivanus was 7 years. These preliminary estimates of ages were higher than anticipated and indicate a fairly stable age-structure for these species. Previous work has suggested that changes in predator abundance can affect prey population dynamics. Therefore, monitoring the prey species could provide information that can be used to determine the status of the predators in areas of differing regulatory regimes.