MANIFESTATION OF GROUP EFFECT IN RAINBOW TROUT (Oncorhynhus mykis, Walbaum) UNDER STRESS CONDITIONS

The main task of the study was identifying differences in growth parameters of individual trout hatchlings handled alone and in a group. Hatchlings were divided into two groups. The first group of hatchlings of various body length and weight was placed to 25 aquaria, a single fish in each. Another group was placed in three equal aquaria. Body weight and mortality have been recorded. Being in a group was found to compensate effects of stress factors. Isolation is a stress for trout hatchlings; combined with other stress factors, it can be a cause of death. These results indicate close connection between theories of group effect and stress.