Specimens of a skin parasite Argulus coregoni Thorell, 1864 (Branchiura: Argulidae) were collected from two species of salmonids [whitespotted charr, Salvelinus leucomaenis leucomaenis (Pallas, 1814), and masu salmon, Oncorhynchus masou masou (Brevoort, 1856)] in a mountain stream of the Ani Riv- er, a tributary of the Yoneshiro River, and from masu salmon farmed using waters from the Yodo River, a tributary of the Omono River, Akita Prefecture, north- ern Honshu, Japan. This represents the second record of A. coregoni in Akita Prefecture, from which only one record exists of the parasite taken from Ayu, Plecoglossus altivelis altivelis (Temminck and Schle- gel, 1846) (Plecoglossidae), from the middle-reaches of the Yoneshiro River. Argulus coregoni was collected for the first time from wild whitespotted charr in Japan and also from farmed fish in northern Honshu. As pre – viously suggested for A. coregoni in central and west- ern Japan, this parasite is considered to use the salmo- nids and Ayu as its hosts in the upper and middle reaches of the Yoneshiro River as well, respectively.