Abstract
We examined the feeding habits, ontogenetic and seasonal diet variations, and predator size–prey size relationships of common snook, Centropomus undecimalis, in Charlotte Harbor, Florida, through stomach contents analysis. A total of 694 stomachs were extracted from common snook (300–882 mm standard length [SL]) during a 24-month period (March 2000–February 2002); 432 stomachs contained prey items. At least 37 prey taxa were identified, including 19 that had not been previously reported. Fishes made up 71% of the prey by number and 90% by weight. Three prey items made up almost 50% of the diet numerically—Lagodon rhomboides, Anchoa spp., and Farfantepenaeus duorarum. Seven species made up more than 60% of the diet by weight—L. rhomboides, Cynoscion nebulosus, Mugil gyrans, Bairdiella chrysoura, Synodus foetens, Orthopristis chrysoptera, and Mugil cephalus. An ontogenetic shift in prey preference was identified in adult common snook at around 550 mm SL. Smaller individuals (300–549 mm SL) ate more F. duorarum, palaemonid shrimp, cyprinodontids, and Eucinostomus spp. than did larger individuals (550–882 mm SL), which ate more S. foetens, ariids, and sciaenids. Significant, positive relationships between predator size and prey size were observed between common snook and L. rhomboides, O. chrysoptera, portunid crabs, and all fish prey combined. Prey size selection contributed to some seasonal differences in their diet. For example, in winter when L. rhomboides are abundant in the estuary and small in size (mean = 23 mm SL), common snook ate few individuals, but they consumed many during summer when larger L. rhomboides (mean = 51 mm SL) were available. In summary, common snook are opportunistic predators that feed on a wide variety of prey and exploit specific-sized prey that are abundant in their environment.