Trophic plasticity and foraging performance in red drum, Sciaenops ocellatus (Linnaeus)

Matching behavior, morphology, or physiology to current environments based on experience or cues can be an adaptive solution to environmental change. We examined morphological and behavioral plasticity induced by durophagy (consumption of hard foods) in red drum (Sciaenops ocellatus), an ecologically and recreationally important fish species undergoing stock enhancement. At the conclusion of the experiment, we conducted feeding performance trials to address the potential adaptive significance of diet-induced traits. Relative to soft foods, hard food induced a deeper head in the area of the pharyngeal mill, anterio-dorsally shifted eyes, and 8% heavier feeding muscles in juvenile S. ocellatus. These fish initially consumed hard food 2.6 times faster than fish raised on soft food. However, in subsequent feeding trials, handling time rapidly converged until both groups appeared equally efficient. This result indicates that learning may compensate for small magnitude morphological differences within a species. We discuss the importance of performance trials for testing the adaptive significance of induced plasticity and the value of separating behavioral and morphological development in studies of phenotypic plasticity. We conclude with a discussion on the implications of our results for successful supplementation of wild populations.