Foraging in Teleost Fishes

Abstract

A short while observing a feeding fish might give the impression that it would be impossible to understand why behavioural changes occur as they do. A foraging roach (Rutilus rutilus), for example, cruises about its habitat digging into the bottom, snapping at a drifting insect in midwater and plucking at a piece of leaf at the water’s edge. How can these apparently disparate actions be explained by a unified foraging theory? The introduction of evolutionary concepts has helped to provide theories that predict decision rules for foraging animals, the principal concept being that efficient feeders will be favoured by natural selection. By minimising the time spent feeding, a fish will have more time to carry out other activities; alternatively, by minimising the energy spent to capture its prey, a fish will have more food energy left for metabolism and growth. So, time minimisation or energy maximisation are the two ways in which the fish can be efficient as a forager. Following on from this assumption, a number of decision rules can be derived which make predictions about how a fish should behave.