Specific features of thermoregulation behavior in early juveniles of roach Rutilus rutilus under thermogradient conditions

Specific features of thermoregulation behavior were studied, and values of the selected and final selected temperature (25.1°C) for early juveniles of roach Rutilus rutilus aged 11–28 days after hatching were first studied in long-term experiments (16 days). Two periods of the process of thermoselection—transient (selected temperature, up to 7–9 days after the beginning of the experiment) and final (final selected temperature, 8–10 days after the beginning of the experiment)—have been identified. The selection by larval roach of final selected temperature values occurs with use of the adaptation response of “excessive responding.” It was shown that correct determination of final selected temperature values for early juveniles of fish is possible only in long-term experiments (more than 7 days). The obtained results can be used during the analysis of behavior and distribution of larval roach under natural and experimental conditions.