The ontogeny of feeding behavior of larval fishes

The feeding and foraging behaviors of fishes were analyzed using video analysis to examine the development of food acquisition in young fish. Before examining young fish in the laboratory, a survey was made of search behaviors used in nature and of feeding mechanisms in adult fish. The foraging movements and prey capture behavior in young fishes were then examined with the aid of newly developed filming technology.; After the swimming and search behavior of larval clownfish, Amphiprion peraderaion, were recorded, results were analyzed with both conventional means and fractal geometry. Similar to other animals, larval A. perideraion used two search modes: linear movement to locate patches of food and convoluted movement to exploit patches. Fractal analysis discriminated between foraging modes, while other methods did not. Unlike other foraging animals, larval clownfish increased swimming speed when encountering high food abundance, possibly because of size-related hydrodynamic constraints.; An analysis of feeding strikes of first feeding Atlantic salmon, Salmo salar, demonstrated that feeding behavior improved significantly during the first two weeks of feeding. First feeding alevins used a body-ram feeding mode. With increasing experience alevins capture prey more quickly and with greater accuracy, using suction to aid prey capture. Also, although alevins raised on a commercial salmon feed were morphologically advanced over alevins raised on live food, their behavior was developmentally retarded (2-3 days). This indicates: learning is involved in the development of prey capture mechanisms, and hatchery raised fish do not require a long time to learn to capture prey effectively in the wild.; An analysis of first-feeding by larval clownfish of the genus Amphirprion showed that the fish exhibit a transition from body-ram feeding to suction feeding during the first week after hatching, similar to the more primitive salmon. At the onset of exogenous feeding, fish were awkward, tending to have difficulty aiming before prey capture. After several days of feeding, the fish employed a stereotypic feeding behavior that used suction to facilitate prey capture. Morphological evidence agrees that the larvae are capable of using suction as early as the fifth day after hatching. ftn*All degree requirements completed in 1991, but degree will be granted in 1992.