Distribution, life history traits, and ecological significance of bigeye sculpin Triglops nybelini (Cottidae) in Siberian Arctic marine ecosystems

The bigeye sculpin Triglops nybelini (Cottidae) is a widespread and abundant species in the Arctic and the adjacent North Atlantic playing an important ecological role in marine ecosystems. Consuming pelagic and benthic invertebrates and being prey for predatory fish and marine mammals, this species participates in the transfer of energy and organic matter between the lower and upper trophic levels. As a key part of a food web, bigeye sculpin indirectly supports some commercially important fishery resources. In addition, this species is a competitor for the food with polar cod Boreogadus saida and some other sculpins. Meanwhile, the data on its ecology and biology in the Arctic seas remain poorly understood, while there is almost no such data for the Laptev Sea (Siberian Arctic). Habitat characteristics and biological features of the Laptev Sea bigeye sculpin are presented for the first time. This species has been observed throughout the lower shelf and upper continental slope within the entire studied depth range of 110–752 m at bottom temperatures ranging from −1.30 to + 1.38°C. The relative abundance (density) was within 21–653 inds./km². Although dense concentrations of this species have not been observed anywhere, its maximum catches have been recorded within the 550–750 m depth range, which is somewhat deeper than published data on the optimal depths. Individuals aged 3–5 years with a total length of 66–110 mm and a body weight of 2–8 g dominated the studied samples. This species in the Laptev Sea is characterized by the presence of sexual dimorphism in the external morphological characteristics and sizes of mature males and females. Among the fish longer than 95 mm, the proportion of females increased sharply, reaching 100 %, with a total length > 100 mm. Despite the relatively diverse diet composition, the bulk of the diet (89 %) of the bigeye sculpin in the Laptev Sea was composed only of hyperiids and euphausiids concentrated within the near-bottom layer. As the size of this species increases, benthic organisms almost completely disappeared from its diet, and only hyperiids and euphausiids became the main prey. This may suggest that unlike many other sculpins, T. nybelini is a benthopelagic fish.