利根川水系におけるカワヒバリガイLimnoperna fortunei の分布状況

抄録

The spatial distribution of the golden mussel, Limnoperna fortunei, was investigated in the Tone River System from November, 2007, to February, 2008. Investigations were conducted up to 180 km from the mouth of the Tone River and the mussel was found up to 120 km upstream. The highest density sites, where one researcher was able to collect 1820 individuals in 10 minutes, are 26 km from the river mouth. The mussel was also found in some other rivers (the Kokai, Nagato, Kurobe, Hitachitone, and Edo Rivers), ponds and lakes (Lakes Teganuma, Sotonasakaura, Ushikunuma, and Yotaura), and canals. The mussel is thus widely distributed in the Tone River System. The density of the golden mussel in the Tone River rises starting at its confluence point with Ibaraki Prefecture's Kokai River, in which the mussel was found abundantly downstream of the water division facility of the Kasumigaura Canal. This spatial distribution of the mussel suggests that it was introduced from Lake Kasumigaura to the Kokai River through the Kasumigaura Canal.