On prey grouping an predator confusion in artificial fish schools

In two simulation models the benefit of schooling underpredatory pressure is investigated. It appears that if a preda-tor cannot become confused by prey, grouping is seldom ben-eficial. If prey, however, can confuse a predator, schoolingappears to protect prey under a whole range of parameters.Using an evolutionary approach we found that, in the caseof a confusable predator, cohesive groups with a consistentforward movement evolve most frequently, but that millingstationary groups also prove to be effective. We suggest thatthe predator protection in moving and stationary groups relyon different mechanisms, among other things, on a kind ofaltruistic behaviour.