The channel catfish, Ictalurus punctatus, is an invasive alien species introduced from North America. We investigated the present status of the fish in Japan and found that it is widely distributed in the Abukuma, Tone, and Yahagi River systems, as well as in Lake Shimokotori. In 2008 and 2009, several channel catfish were also caught in Lake Hinuma and the Miya and Seta Rivers. We concluded that the distribution of channel catfish has rapidly expanded within natural rivers during the past several years. To avoid severe damage imposed by channel catfish to the river ecosystems and inland fisheries of Japan, risk assessments and examinations of the ecological characteristics and methods of capture of this fish species are urgently required.
