Evolutionary trends in fish schools in heterogeneous environments

Individual-based modelling has contributed substantially to the understanding of fish schooling behaviour. Schooling is considered to grant several advantages, such as increased defense against predators and increased foraging success. Whereas the former has been well studied with empirical investigations and different modelling approaches, the latter has not received as much attention. Foraging success is considerably influenced by the emergent property of schools to locate and exploit heterogeneously distributed resources more efficiently than solitary fish. However, successful resource exploitation depends on individual fish properties as well as properties of the school in relation to patch size and spatial distribution of resources. Thus, schooling will be favourable in specific environmental conditions and less efficient in others. We use an individual-based model to assess the foraging efficiency of schooling compared to individual food search under different spatio-temporal distributions of food resources in a dynamic environment. Allowing agents' behaviour to evolve either towards schooling or towards individualism, we demonstrate the adaptation of population characteristics to a particular spatial and temporal distribution of food patches. With our model we show that the environmental configuration of food patches is crucial for schooling fish to be more efficient in foraging. Moreover, patch size must be considerably larger than the extent of the school but small enough for patch boundaries to take effect. The model contributes to a better understanding of the relationships among spatial dynamics and the driving forces behind behavioural adaptation of trophic strategies in schooling fish. (C) 2015 Elsevier B.V. All rights reserved.