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    A revised estimate of short-term yield for the mackerel icefish (Champsocephalus gunnari) off Heard Island based on a trawl survey in 1998

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    A. Constable and D. Williams (Australia)
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    A random stratified trawl survey of Mackerel icefish in 2 populations (Plateau and Shell Bank) in the vicinity of Heard Island enabled a revised estimate of yield for the coming 2 seasons in 1999 and 2000. While the abundances of icefish are lower in 1998 than in 1997, the Age 3 and Age 4 cohorts are still sufficiently strong to provide for a yield greater than estimates of the long term precautionary yield. Estimates of yield for the Heard Island Plateau population are 732 tonnes for 1999 and 518 tonnes for 2000. These figures may need to be re-evaluated in light of known catches in the 1998 season since the survey. Estimates of yield were not made for Shell Bank given the very low abundance in this population. Unlike the previous 3 years, the Age 2 cohort in 1998 is very weak and is expected to contribute little to the biomass in subsequent years. If recruitment to Age 2 in 1999 is also weak then the fishery in 2000 will be predominantly on Age 5 fish. After this time, catch limits may need to be set at an estimate of a long term precautionary level and be maintained thereafter unless a further survey again showed that abundant cohorts had been recruited.