CCAMLR

The management of Champsocephalus gunnari at South Georgia is complicated by the likelihood of substantial periodic variation in natural mortality rates. These may be associated with increased consumption of icefish by Antarctic fur seals in years of poor krill availability. Thus natural mortality of icefish may, in some years, increase by a large factor (assumed here to be 4) declining to normal levels again when krill return. A scheme is elaborated that would use information from studies on krill and predators undertaken as part of CEMP to interpret or modify information from commercial fisheries and research surveys leading to estimates of stock biomass. An extension of this scheme would use predictions of coming periods of krill scarcity as early warnings of increased natural mortality on icefish. This scheme would require greater quantitative knowledge of food web dynamics within the South Georgia ecosystem than we have at present. There is therefore a need for an interim approach to setting precautionary catch limits for this fishery. An approach based on the general yield model is described, which can be used to calculate an appropriate proportion of an estimate of Bo which could be taken by fishing, under conditions where M is assumed to be highly variable from year to year.

Haul by haul data acquired by the UK from longline fishing for Dissostichus eleginoides around South Georgia were compared with data reported to CCAMLR and held in CCAMLR's longline database (database C2). Some instances of incomplete reporting were identified, where blocks of data appear to be missing from the CCAMLR database. One instance was identified of multiple hauls being submitted as single records. A number of hauls yielding zero catches present in the data acquired by the UK have not been reported to CCAMLR. In 1996 less than 10% of the hauls showed large discrepancies between the two datasets, with many of the records for individual fields being identical. The number of discrepancies between the CCAMLR database and the data acquired by the UK declined from 1994 to 1996. However, there were a considerable number of discrepancies between the CCAMLR data and those acquired by the UK in reporting bycatch and incidental mortality of birds.

A new fishery was declared for Dissostichus spp in Division 58.4.3 for the 1996197 season. Results of a brief survey by an Australian vessel are presented, but catches were very low. A new proposal for an exploratory fishery in Division 58.4.3 is presented. This involves a random stratified trawl survey to be undertaken in parallel with commercial exploration, and the collection of a comprehensive data set from both the survey and commercial operations.