The fish louse Argulus coregoni from Oncorhynchus masou ishikawae (Salmonidae) cultured in Shikoku, western Japan, with a list of occurrence records of A. coregoni from fishes reared in Japan

Argulus coregoni Thorell, 1864 is briefly described based on specimens from the body surface of amago salmon, Oncorhynchus masou ishikawae Jordan & McGregor, 1925, cultured at a trout farm in Tokushima Prefecture, Shikoku, western Japan. This represents the first confirmed record of A. coregoni from farmed salmonids in Shikoku. A list of occurrence records of A. coregoni from fishes reared in Japan is also provided based on the literature published between 1950 and 2019. The species has so far been reported from three species and two subspecies of salmonids and one species of plecoglossid reared at 14 sites in 10 prefectures (Tochigi, Tokyo, Nagano, Ishikawa, Gifu, Aichi, Wakayama, Hyogo, Tokushima, and Yamaguchi). Most of these sites were governmental or research facilities, and it is evident that little attention has been paid to A. coregoni at commercial tout farms. The species is considered to occur at more trout farms in Japan.