Biological Characteristics of the Great Sculpin Myoxocephalus polyacanthocephalus (Cottidae) from Pacific Waters off the Kuril Islands and Southeastern Kamchatka in Autumn Period

Abstract

The spatial distribution, size-sex composition, feeding of Myoxocephalus polyacanthocephalus and accompanying species in the Pacific waters off the northern Kuril Islands and southeastern Kamchatka in the autumn period are considered. In August–November 1997, this species was represented in catches by individuals with a length of 30-89 (on average 47.8 ± 0.5) cm and a body weight of 300–11000 (2321 ± 90) g. Females dominated over males; the sex ratio was 1.2 : 1.0. The relationship between the body weight and length of great sculpin is described by the exponential equation: W = 0.0031FL3.446 (R2 = 0.935). The food spectrum of great sculpin includes fish (56.2% of the diet), mainly the walleye pollock Gadus chalcogrammus and Atka mackerel Pleurogrammus monopterygius (19.9 and 11.9%, respectively); fish processing wastes (19.6%), mainly heads of Atka mackerel (12.2%); as well as decapods (18.6%), mainly the snow crab Chionoecetes opilio (14.1%). As great sculpin grow, decapods are replaced by fish in the diet and walleye pollock is replaced by Atka mackerel and Liparidae. The size and sex composition and feeding patterns of great sculpin as well as the species composition of the accompanying species differed in some parts of the surveyed area. The co-occurrence of great sculpin with walleye pollock and the northern rock sole Lepidopsetta polyxystra was 100%.