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.
We examined the effect of binary coded wire tagging on oxygen consumption rates of seven species of seawater fish and three species of freshwater fish. Nine were found that one hour after tagging, the oxygen consumption rates of tagged fish were 50-80% higher than those of non-tagged controls. The oxygen consumption rates of Girella melanichty, Oreochromis mossambicus and Carassius auratus returned to the original level six to seven days after tagging. Additionally, no effect was found on both growth and mortality rates in a long term observation.