DIFFERENCE IN SWIMMING BEHAVIOR BETWEEN ORYZIAS LATIPES AND GAMBUSIA AFFINIS IN A CHANNEL WITH REFUGES

Abstract

 The Japanese medaka (Oryzias latipes) is an endangered species. The mosquitofish (Gambusia affinis) is an invasive species native to North America that is designated as an invasive alien species in Japan. In this study, laboratory experiments were conducted to clarify the difference in the avoidance behavior and use of refuge against running water between Japanese medaka and mosquitofish, by observing their behaviors with respect to swimming speed, swimming distance and residence time in the observation section.

 The results showed that the Japanese medaka changed its swimming behavior according to the flow velocity. On the other hand, no rheotactic reactions were observed of the mosquitofish, and refuges were used even at a low flow velocity. In conclusion, we believe that the Japanese medaka is able to adapt to changes in water flow, and that the mosquitofish tends to be more lentic than the Japanese medaka.