抄録
A microsporidiosis of salmonid had previously been found in limited districts in Hokkaido, i. e. River Chitose and Lake Tokito. In September of 1977, a new epizootic area of this disease was confirmed by the author at Lake Akan in the eastern Hokkaido. In this report, the similarity of biological environment among epizootic areas especially the habitability for fresh pearl mussel, Margaritifra laevis is discussed.
