Distribution and biology of understudied slender eelblenny Lumpenus fabricii (Stichaeidae, Teleostei) in two Siberian Arctic seas, with comparative data on some other ground fishes

Based on the materials collected in August–September 2019 during the Transarctic expedition onboard R/V “Professor Levanidov”, new data on the spatial and vertical distributions, bottom temperatures of habitat and biological features (size-age and size-sex structures, maturation, fecundity, diet composition) of the poorly studied slender eelblenny Lumpenus fabricii in the Chukchi and Kara seas are presented. In the Chukchi Sea, its main catches were recorded in the southwestern part of the sea (northeast of the Bering Strait) at shallower depths (100 m) and bottom temperatures 3.0 to 5.0 °C. In the Kara Sea, this species was found in catches mainly on the southwestern shelf of the sea (the western coast of the Yamal Peninsula and outer Baidaratskaya Bay) at depths shallower 25 m and bottom temperatures around 1.5 °C. Its individuals aged 4–9 years with a total length of 102–268 mm and a body weight of 3.1–28.3 g were recorded in trawl catches. However, 5–6-year–old fish 111–130 mm long weighing 4–6 g dominated in the Chukchi Sea, while individuals aged 6–7 years with a total length of 141–200 mm and a body weight of 8–16 g were most abundant in the Kara Sea. This species is characterized by sexual dimorphism in sizes, i.e. males are larger than females, whose fecundity varies from 115 to 436 eggs. Among individuals longer than 180 mm, the proportion of females decreases sharply, reaching zero in fish longer than 220 mm. As a result, the largest individuals of this species are represented exclusively by males. Slender eelblenny is a consumer of small- and medium-sized benthos, the main prey of which in the Chukchi and Kara seas are small benthic invertebrates (mostly polychaete worms and amphipods). Comparison with other common ground fishes in the study area showed that slender eelblenny in the Siberian Arctic seas occupies specific ecological niche with different depths and bottom temperatures. The diet of this species was similar to that of the Arctic staghorn sculpin Gymnocanthus tricuspis and the Arctic alligatorfish Aspidophoroides olrikii but differed from that of the ribbed sculpin Triglops pingelii and the bigeye sculpin T. nybelini.