Spatial Structure of Deep-Sea Pelagial Ichthyocenes in the Northern Weddell Sea (Powell Basin) and Brunsfield Strait in Summer 2020 and 2022

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Abstract
—A review of the composition and structure of deep-sea pelagic ichthyocenes in the Bransfield Strait and northern Weddell Sea (Powell Basin) in the Atlantic sector of the Southern Ocean is presented. The material was obtained in summer 2020 and 2022 at 26 stations at layers from 120–0 to 2200–0 m. Nine hundred one specimens of juveniles and adult fishes belonging to 19 species from 10 families were collected. Statistical analysis made it possible to identify four significantly different regions in which the dominant ichthyocenes were located in waters of different origin. These ichthyocenes are poor in the number of identified species, but often quite numerous. Relatively shallow-water representatives of the families Bathydraconidae, Channichthyidae, Liparidae, and Nototheniidae, endemic to the shelf and slope of Antarctica, dominated in the area of the Antarctic Strait and on the shelf of the Antarctic Peninsula. At the same time in the Bransfield Strait, the abyssal basin of the Powell Basin, and in the pelagic zone above deep-sea ridges and trenches bordering it from the north, meso- and bathypelagic fish from the families Mycthophidae, Bathylagidae, Gonostomatidae, Paralepididae, and Scopelarchidae prevailed. Near the northern boundary of the Powell Basin, the number of mesobatypelagic species and their average abundance were higher than in its central part (11 vs. 7 species and 63.5 vs. 84.1 sp./100 m2). In the central part of the basin, Bathylagus antarcticus dominated, with an average share of 40% in catches and 28.8 sp./100 m2, while in the northern part of the basin, Electrona antarctica dominated, with an average share of 33%, 27.4 sp./100 m2.

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