Tomtate Population Demographics and Trophic Ecology in the Northern Gulf of Mexico

Thursday, September 12, 2013: 3:20 PM
Pope (Statehouse Convention Center)
Michael J. Norberg , Marine Sciences, University of South Alabama, Mobile, AL
William F. Patterson III , Marine Sciences, University of South Alabama, Dauphin Island Sea Lab, Dauphin Island, AL
The tomtate, Haemulon aurolineatum, is a small haemulid reef fish widespread in the northern Gulf of Mexico, but little is known about its trophic ecology or population dynamics. Objectives of this study were to test for differences in tomtate abundance, trophic ecology, and population dynamics between natural and artificial reefs. The difference between tomtate densities on AR versus NR was not significant (ANOVA, = 0.56). There was also no significant relationship between length (TL) and δ15N (GLM, p = 0.17), thus no shift in trophic position detected across the size range (180-270 mm TL) examined. Differences in δ34S isotope indicate tomtate on NR foraged on more benthic than pelagic prey than tomtate on AR. Individuals that were aged (n=563) ranged from 60 to 290 mm TL and 0 to 14 y. A von Bertalanffy growth function fit to those data resulted in the function Lt = 242[1-e-0.664 (t +0.11)]. Estimates of instantaneous total mortality (Z), natural mortality (M) and fishing mortality (F) were 0.41, 0.30 and 0.11 y-1, respectively. Tomtate are known to be captured and used as bait in the nGOM reef fish fishery. An F:M ratio of 0.36 suggests fishing has a moderate impact on nGOM tomtate population.