摘要：The mercury mine in Uda Country was closed in February 1974. Change of mercury accumulation in Oikawa (Zacco platyps) that lived in Hono and Uda River was examined during 1974 to 1976. Mercury accumulation was high every year near the drain exit of the mercury mine and the junction of rivers. At the every investigation station, mercury accumulation was on the decrease every year, and the decreasing rate of mercury accumulation was higher near the drain exit of the mercury mine and junction of rivers. The decreasing rate of methylmercury was lower than that of total mercury.
