Age–length composition of mackerel icefish (Champsocephalus gunnari, Perciformes, Notothenioidei, Channichthyidae) from different parts of the South Georgia shelf
Biostatistical data obtained by Soviet research and commercial vessels from 1970 to 1991 have been used to determine the age-length composition of mackerel icefish (Champsocephalus gunnari) from different parts of the South Georgia area. An analysis of the spatial distribution of C. gunnari size and age groups over the eastern, northern, western and southern parts of the shelf, and near Shag Rocks, revealed a similar age-length composition for young fish inhabiting areas to the west of the island and near Shag Rocks. Differences were observed between those those two groups and the eastern group. The larger number of mature fish in the west is related to the migration of maturing individuals from the eastern and western parts of the area. It is implied that part of tlne western group migrates towards Shag Rocks at the age of 2-3 years. It has been found that, by number, recruits represent the largest part of the population, whether a fishery is operating or not. As a result of this, as well as the species' ability to live not only in off-bottom, but also in pelagic waters, an earlier age of sexual maturity compared to other nototheniids, and favourable oceanographic conditions, the C. gunnari stock could potentially recover quickly from declines in stock size and may become abundant in the area, as has been demonstrated on several occasions in the 1970s and 1980s.