Distribution of amphidromous and landlocked forms of ayu Plecoglossus altivelis in the Yodo River system

Abstract

　In the Yodo River system, where various ayu stocks are released, it is not clear which forms of ayu, amphidromous or landlocked, are established and contribute to reproduction. Microsatellite DNA polymorphism analysis was used to determine the phylogeny of spawning stocks, estuarine and coastal larvae and juveniles, and upstream migrants in the Yodo River system to elucidate their reproductive contribution and presence. In all the living seasons, we confirmed that there were mainly individuals belonging to the amphidromous form, but we also confirmed individuals from the landlocked form, and it became clear that there was a high possibility that ayu from the landlocked form also reproduced.