Schooling in fish  (Page 2/10)

Schooling was initially thought to be a behavior with little structure or adaptive significance (Keenleyside 1955), however further study has revealed an intricate and developed structure behind the school. Individuals are capable of plastic behavior in terms of when and where they school. The banded killifish ( Fundulus Diaphanus ), which live in isolated populations, stay in close proximity of one another and when there is a shortage of food or a predation threat, they quickly band together and school. Staying close together affords them this flexibility and is seen as a function of external stimuli (Hoare et al 2004). Scientists have discovered that schools are much more complex in their structure than originally thought, lacking almost any randomness. Instead, individuals compete for positions within the school, with edge positions typically falling to those with the least fitness (Hamilton 1970). These schools are often are controlled by signals within the group from neighbor to neighbor. The signals are used to direct traffic, indicate the presence of food, aid recognition of school members, and send out alarm calls in the face of predators (Magurran 1994). Consequently, the reactions to finding food or encountering a predator are well orchestrated and coordinated. Fish may or may not school, and these choices depend on food availability, predator density, and sometimes for females, even the level of sexual harassment present. Here we examine the evolutionary reasons for schools, how these schools are able to adapt to environmental changes, and the known aspects of school mechanics .