Comparison of the Territorial Behavior between Amphidromous and Landlocked Forms by Water Temperature in Ayu, Plecoglossus altivelis

Abstract

The territorial behavior of the two geographical races of ayu Plecoglossus altivelis, i. e. the amphidromous and landlocked forms was examined under the conditions of different water temperatures. The percentages of cases in which territory was established were relatively high in the higher temperature in the amphidromous from, and in the lower temperature in the landlocked form. The degree of aggressivity measured by the frequency of self-attacks against a mirror, showed similar tendency with the former experiment for the two races concerning with the water temperature. Artificially propagated clonal fish from the amphidromous form showed similar temperature-specific territoriality as the wild fish of the amphidromous form. These results suggest that the difference in territoriality and aggressivity between these two geographical races reflect the genetic difference in temperature-specificity.