Distribution, Size and Sex Composition of Gymnocanthus pistilliger (Cottidae) off the Western Coast of Kamchatka in the Summer Period and Modern State of its Resources

Abstract

In the summer period of 2017, the threaded sculpin Gymnocanthus pistilliger occurred at depths from 14 (minimum depth of trawling) to 64 m in the Sea of Okhotsk off the western coast of Kamchatka. Areas of the maximum G. pistilliger concentrations are only partially similar in terms of fish mass and abundance. The maximum average catches in terms of biomass were recoded between 55° and 56° N, where a high abundance of the species was also recorded. The maximum average catches in terms of abundance were obtained southerly, between 53° and 54° N. The species is the most common and abundant to the depths of 40−50 m. The length of specimens varies within 6−26 (on average 18.3) cm. The ratio of males to females is 0.4 : 1. The smallest sizes of specimens of both sexes were recorded in the depth range of 14−20 m; the average sizes of males and females increase with depth. In the summer period, G. pistilliger occurs in a wide temperature range between 0.4 and 12.1°С on the West Kamchatka shelf. The highest catches of the species were recorded at the temperature of 1.0−3.5°С in the main part of the bathymetric interval, and at 3.5−6.0°С in a shallow zone. According to the results of summer surveys off the western coast of Kamchatka the estimated abundance of G. pistilliger was 146 million ind., and the biomass was 11200 t.