Swimming and search behaviour in clownfish, Amphiprion perideraion, larvae

Abstract

The swimming behaviour and search patterns of pink clownfish larvae, Amphiprion perideraion, were examined using a novel filming apparatus that permits three-dimensional tracking of free swimming zooplankters. Analysis of the resulting search paths included swimming speed and average turning angle, as well as a new approach to the study of search dynamics, fractal analysis. Amphiprion perideraion larvae display a clear shift in behaviour at the onset of feeding, with a drop in overall complexity of their swimming paths and an increase in their swimming speed. Similar to other foraging animals, clownfish larvae display at least two search modes after the onset of feeding: a highly linear ranging mode used to locate patches of food and a highly complex, convoluted searching mode used to exploit those patches once they are located. Conventional analysis did not adequately discriminate between foraging modes, creating the need for fractal analysis. Unlike other foraging animals, clownfish larvae increase swimming speed when they encounter patches of high food abundance. This response is proposed to be the result of hydrodynamic constraints imposed upon the fish because of their relatively small size.