Survival of a landlocked form of ayu fry released in the Shou River

摘要

Fin clipped ayu, Plecoglossus altivelis, fry of landlocked form, were released in the Shou River from May to June, 1992 to 1996, and some were recaptured near the spawning grounds each year between September 20 and November 4. The spawning of landlocked form reared in the pond started from September 16 to September 21, and that of amphidromous form started from September 29 to October 7. It is suggested that cross-mating between landlocked and amphidromous forms occurred partly after early October in the Shou River.