Growth of mackerel icefish (Champsocephalus gunnari) and age-size composition of populations in subarea of South Georgia

Age, growth rate and age composition of icefish catches in subareas 48.3, 48.2, 48.1 were studied for different periods. The analysis of age composition of icefish in subarea 48.3 showed that the catches consisted mainly of individuals of 2-4 age groups, where more than 60% were represented by fish of two contiguous age groups. It was shown that in the 1980s during a number of years the catches were based on fish of two contiguous year classes, strong 1984 year class and middle 1983 year class. These year classes appeared against a background of the intensive icefish fishery, and krill biomass, judging from the catches, was rather low. Possibly, the abundance of one or another icefish year class in subarea 48.3 depends on many factors, among which it it difficult to determine the most important factors now. A comparative analysis of icefish growth in subarea 48.3 based on data collected in different periods of fishery revealed a substantial interannual variability. The comparison of the growth rate of fish caught in 1978 in subareas 48.3 and 48.2 and that of fish caught in 1986 in subareas 48.3 and 48.1 did not reveal any significant differences. The relatively high growth rate of icefish in subareas 48.3 and 48.2 in 1978 compared with 1985 may indicate on the common factors affected the icefish growth in different regions of the South Atlantic in that time.