Assessments of the abundance and potential yield of mackerel icefish (Champsocephalus gunnari) populations at Heard Island are developed from the results of four scientific surveys conducted in 1990, 1992, 1993 and 1997. The assessments include estimates of all the parameters required, based on the data collected during the surveys, including growth curves, natural mortality, ages and sizes of maturity and a weight length relationship. The results show that characteristics of icefish populations on the Heard plateau are sufficiently different from those on Shell Bank for them to be managed separately. Precautionary catch limits calculated using the Generalised Yield model are found to be 180 tonnes for the plateau and 18 tonnes for Shell Bank. An assessment based on the results of a survey conducted at the end of the 1997 fishing season would allow for a catch limit on the Heard plateau of 900 tonnes in the 1997/98 season and 600 tonnes in 1998/99.