Armored fish in cold polar waters: New information on the Arctic alligatorfish Aspidophoroides olrikii (Agonidae, Perciformes, Teleostei) from the Kara Sea (Siberian Arctic)

Data on the spatial and vertical distributions, temperature regime of habitat, size-age and, size-sex structure of Arctic alligatorfish Aspidophoroides olrikii in the Kara Sea based on a recent trawl survey are presented. A total of 104 specimens were caught from 9 (out of 55) trawl stations. Maximum catches of this species were recorded north of the Yamal Peninsula (74°11′–74°25′ N, 69°27′–71°59′E) at depths of 18–21 m in the range of bottom temperatures from -1.49 to -0.96 °C. In trawl catches, individuals aged 2–6 years with a total length of 39–76 mm with a body weight of 0.25–2.91 g were recorded, but fish up to 50 mm length with a body weight of less than 0.5 g dominated. Among individuals over 68 mm in length, the proportion of females increased sharply, reaching 100% with a length of more than 75 mm. It was found that males and females of the Arctic alligatorfish become sexually mature in the third year of life, the former at a length of 47–48 mm, the latter at 52–58 mm long. Maturation of the half males and females occurs in the fourth year with the length of 52–58 mm and 61–63 mm respectively. It is shown that this species is a mesobentophagus, the main prey of all its individuals are amphipods, which make up about 95% of the diet. However, as A. olrikii grows, the number and size of amphipods consumed increase.