SENSORY INFORMATION AND THE ORGANIZATION OF BEHAVIOR IN A SHOALING CYPRINID FISH

Quantitative comparison of the behavior of bream, Abramis brama (L.), under 4 controlled conditions indicates that the organization and spectrum of behaviors of this shoaling teleost fish differ according to the sensory information it receives from a conspecific. Bream are true social animals, behaving normally only when in full sensory contact, in contrast to earlier suggestions that vision alone could mediate fish social behavior. Both lateral line and vision are employed simultaneously to maintain individual distance. Mirror images, fish images and real fish are distinguished at different distances, but only the abnormal feedback from an approachable mirror is eventually compensated for, indicating considerable central processing. Lack of lateral line input causes a greater synchrony with the image of a neighbor, reinforcing a similar recent finding in schooling saithe. Bream in full sensory contact are more likely to make forays away from each other. The use of shoal as a more helpful general term for a social group of fish (equivalent to flock in birds) is recommended, and the term school should be restricted to polarized synchronized groups. Lateral line, vision and olfaction are used in shoals, but probably only lateral line and vision in the maintenance of schooling.