Variations in condition indices of mackerel icefish at South Georgia from 1972 to 1997

Mackerel icefish (Champsocephalus gunnari) are widespread on the South Geor gia shelf, Antarctica, and have been fished commercially since the early 19 70s. They are known to feed predominantly on krill. An index of condition w hich uses the ratio of the measured total mass to the estimated mass is sho wn to provide a good indicator of local krill density. The index is likely to be little affected by the reproductive cycle unless there is high krill availability during the months around the spawning time, and even then the effect is much less than the highest observed values, The condition index r esponds rapidly to changes in krill density and therefore can provide indic ations of short-term variations in krill availability. Condition index prov ides a useful proxy for krill density and is likely to be of considerable v alue in interpreting the results from ecosystem assessments such as that in progress under the auspices of CCAMLR.