Spatial distribution of an exotic mussel, Limnoperna fortunei, in Lake Biwa and connected waters in western Japan

The spatial distribution and abundance of the exotic mussel Limnoperna fortunei was investigated along the shore of Lake Biwa and in connected waterways from November, 2008, to November, 2009. The mussel was commonly and abundantly found along the lake's shore except for the western side of Northern Lake Biwa, and it was first recorded for the first time in neighboring Lake Yogo, as well as at Chikubu Island and Okinoshiraishi Island within Northern Lake Biwa. The highest density of the mussel was found in Southern Lake Biwa and also in Lake Yogo, places where high concentrations of chlorophyll-a occur for much of the year. The mussel was found in the Seta, Uji, and Yodo Rivers comprising the outflow from Southern Lake Biwa, and also in their tributary the Kizu River. Seeds of mussel populations in the Kizu River may be supplied from the Takayama Dam upstream.