抄録
Since 2002, the catch of Corbicula japonica has decreased in Lake Ogawara, which is located in the southeast of Aomori prefecture. The lake is one of the representative brackish lakes. The cause of the decrease until 2005 is the catch limit by Ogawarako fisheries cooperative association. The catch limit were due to decreases of the stock biomass of Corbicula japonica in the lake. After that, in 2006 and 2007, the stock biomass increased. In recent years, the commercial size is over 18.5mm in length, which has not increase. The purpose of this study is to investigate the cause of the decrease in the biomass over 18.5mm in length in recent years, and to consider the relationship between the bottom sediment, water quality and the stock biomass of Corbicula japonica in the lake. The results show that the habitat for Corbicula japonica have become small, according to the values of dissolved oxygen, the mud content in sand and the ignition loss.
