Size-specific protection against predation by fish in swarming waterfleas,Bosmina longispina

When feeding on non-swarming waterflea prey, sticklebacks, Gasterosteus aculeatus, selected larger items. However, when feeding on swarming prey, the fish fed mainly at the edges of the swarms and smaller items were consumed. This selection of small prey items can be explained by the fact that when attacked by a stickleback the waterfleas escaped towards the centre of the swarm, larger individuals more quickly than smaller ones, thus leaving the stickleback with smaller than average prey at the edge of the swarm.