Notes on Champsocephalus gunnari biology, availability, diet and spatial distribution in the South Shetland and South Orkney Islands (Subareas 48.1 and 48.2)

Stocks of the mackerel icefish Champsocephalus gunnari in the Southern Scotia arc region of the Southern Ocean (CCAMLR Subarea 48.1 & 48.2) have several different biological characteristics than stocks in the Northern Scotia Arc. The history of commercial C. gunnari exploitation in the Southern Scotia Arc was short lived and intense, and led to the collapse of the stocks. Stocks in this region are presently very low relative to historical levels, particularly around the South Orkney Islands. Aspects of the biology, patterns of distribution, maturity, diet, and abundance based on recent scientific surveys conducted by the U.S. AMLR Program are presented. During the month of March, the species appears to use the shelf areas around Elephant Island and the lower South Shetland Islands differently, with juveniles favoring the western shelf of Elephant Islands and larger, more mature fish favoring areas on western and northwestern parts of the Elephant Island shelf and the lower South Shetland Islands near Livingston Island. The dietary composition of C. gunnari appears to be more diverse in the South Orkney Islands, while their diet in the South Shetland Islands is almost entirely krill (Euphausia superba). The effect of E. superba density on the spatial distributions of C. gunnari abundance, size, and feeding patterns in the South Shetland Islands for the 2001 survey is examined. Preliminary results suggest a complex relationship between spatial distribution, size composition, and feeding intensity of C. gunnari and prey density patterns.