Morphological Heterogeneity of Sakhalin Sculpin Cottus amblystomopsis Schmidt, 1904 from Sakhalin, Kunashir, Iturup and Hokkaido

The article is devoted to the study of intraspecific variability of the Sakhalin sculpin, Cottus amblystomopsis (Cottidae). This species has been described from the rivers of Southern Sakhalin and is found on the islands of the southern part of the Kuril Archipelago, as well as on Hokkaido. A morphological study of Sakhalin sculpin across its entire range has not yet been undertaken. To determine morphological differences between various island populations of this species, a complex of morphometric characters (plastic and meristic) was analyzed using multidimensional statistical methods. Based on the results of the study, three forms of Cottus amblystomopsis were identified: 1) the typical form inhabiting the river systems of South Sakhalin, Kunashir and Hokkaido; 2) the Iturup form; and 3) the North Sakhalin form (from the Malaya Aleksandrovka River).