Schooling affects the feeding success of Australian salmon (Arripis trutta) when preying on mysid swarms (Paramesopodopsis rufa)

Abstract

When feeding on mysid swarms (Paramesopodopsis rufa), juvenile Australian salmon (Arripis trutta) had higher rates of successful attacks when foraging in a group of six fish (55% total advances) than when foraging alone (39% total advances). Six schooling fish had lower approach rates than solitary fish (25% and 37% of total advances, respectively). This result indicated that schooling fish were better at reducing the confusion effect of swarming prey, resulting in more efficient feeding. In larger areas, schools achieved higher rates of successful attacks (19 prey/fish in the large tank, compared with 11 prey/fish in the smaller tank). There was no influence on the feeding success of individual fish when changes were made to the number of prey presented to each fish. Nearest neighbour distances were smallest in the absence of prey, and increased with the introduction of prey and again in an attack sequence. Six fish schooled more cohesively than three fish, indicating increased benefits of schooling in larger groups that contribute to advanced vigilance and foraging techniques.