INFLUENCE OF SUBSTRATE COLOR AND GROUP-SI ZE ON MOTOR-ACTIVITY OF CICHLASOMA-NIGROFASCIATUM (CICHLIDAE, PERCIFORMES) JUVENILES

Relations between the background motor activity of Cichlasoma nigrofas ciatum juveniles and the bottom colour and the group size were studied . Activity of fishes was compared in aquaria with bottoms of different colour (black, white, striped, divided into black and white). The mot or activity in isolated fishes was lowest in the aquarium with black b ottom, increasing in the aquaria with white and striped ones. The high est motor activity was registered in the aquarium with the bottom divi ded into white and black halves. In the groups composed of two and thr ee individuals the motor activity was lower than in isolated ones, in the groups of four fishes it was tower than in isolated ones, in the g roups of four fishes it was higher. This correlation is characteristic of all the investigated substrates except striped one. The striped su bstrate retards the motor activity of fishes in direct proportion to t he number of individuals in the group. The results obtained are of val ue in methodical aspect since they allow to manipulate the average lev el of motor activity of fishes using background stimuli.