Mechanisms of Schooling Behavior of Fish

Abstract

The basic mechanisms of schooling behavior of fish, which is a genetically fixed species character, have been considered. The intention of schooling fish to unite with individuals of their own species or with fish that are similar in shape, color and motor activity pattern (schooling reaction) is an innate reflex that manifests itself in natural and artificial environments in individuals with different individual experiences. The intention to unite is expressed the stronger, the more schooling behavior is characteristic of fish. The larger the school, the more attractive it is for fish. To choose a school for association, it is enough that it be 2–3 times larger than the rest. This difference decreases with an increase in the number of fish in schools, with the threat of a predator attack and other stresses. In juveniles, the intention to unite with larger schools is more pronounced than in adult fish. Given a choice, fish prefer individuals of their own species and fish similar in size and color. Imitation is an unconditioned reflex, which is another important mechanism of school behavior. Imitative reactions are most pronounced in schooling fish, but their manifestation is possible if the imitated and imitating fish are conspecific and close in size. An innate optomotor reaction (following reflex) ensures that fish maintain a single school during movements and rapid maneuvering. Schooling coordination is achieved by focusing on the actions of one of the closest partners, and the parallel arrangement of fish is achieved by accurately following the leading partner. Recognition of individuals of their own species, mutual orientation and coordination of actions of fish is facilitated by schooling coloration—spots, stripes and patterns on the body, head and fins, differing in position, size, shape, color, brightness and other details. Important visual landmarks are the contrasting eyes of school partners. Schooling coloration is not present in all schooling fish. In many species, schooling coloration changes as the fish grow and develop.