Distribution of mackerel icefish (Champsocephalus gunnari) (Channichthyidae) around South Georgia at various stages of its life cycle
The distribution of mackerel icefish (Champsocephalus gunnari) around South Georgia (FAO Statistical Subarea 48.3) at various stages of its life cycle was studied using material collected by AtlantNIRO from 1970 to 1991. This study took into account the spatial–temporal variability of C. gunnari. Young fish of the first age group (<15 cm in length) were mainly found in the southern part of the study area, immature fish (15–25 cm) in the east and southwest, and adults (25–39 cm) in the north. The distribution of C. gunnari changes during its life cycle. Fish larvae inhabit the upper 100 m layer of pelagic waters. Young fish (<6 cm) were mainly observed near the bottom and at depths of up to 75 m from the bottom. Young fish undertake vertical migrations into the water column during the day and return to the bottom layers at night. Immature fish were found to be distributed throughout the water column at all times of the day, but they also undertake vertical diurnal migrations similar to those of mature fish. Mature fish were found near the bottom during the day and in the water column at night. Larger fish (>40 cm) did not undertake vertical migrations. Variations found in the depth distribution of C. gunnari relate both to fish length and season.