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.

This paper provides an assessment of the long-term annual yield for three species caught as by-catch in the commercial trawl fisheries in the Heard Island area (Statistical SubArea 58.5.2): Channichthys rhinoceratus, Lepidonotothen squamifrons and skates (Bathyraja spp.). These assessments were undertaken with the aim of examining the potential for the commercial trawl fisheries to significantly affect the spawning biomass of these stocks in the longer term. The long-term annual yield for each of the three species were estimated using the generalised yield model developed for WG-FSA, based on survey data obtained from the region in 1990-1993. Values for missing input parameters were obtained from the literature. The second part of the analysis examined the amount of each species caught in the commercial operations, the nature of the trawl operations in which they were caught and the effectiveness of current by-catch provisions in CCAMLR to ensure the status of these species is not affected by these fisheries. The estimates of long term annual yields for Channichthys rhinoceratus, Lepidonotothen squamifrons and skates were 69-97 tonnes (average 80 t), 7-91 1 tonnes (average 325 t) and 50-210 tonnes (average 120 t) respectively. Notably, the by-catch in 1997 did not exceed the lowest estimates of yield for each species. The results indicate that the current commercial trawl fisheries around Heard Island are unlikely to be negatively affecting these stocks. Notably, the large majority of infringements of the 5% by-catch rule in CCAMLR were caused by very small amounts of by-catch. This occurs, especially in prospecting mode, when the catch of target species is low, and hence the amount of by-catch necessary to trigger the 5% rule is also very low. Most infringements were caused by less than l00kg of by-catch. While the basic role of the by-catch provisions is to protect the by-catch species from over-exploitation combined with protection them from being targetted by commercial operations, the current 5% by-catch rule excludes many areas from prospecting. In order to enable prospecting for commercial aggregations of icefish or toothfish while protecting the by-catch species from excessive fishing effort, the by-catch rule could be modified for the Heard Island area to allow catches of by-catch species of up to 100 kg in any one haul. However, if this level is exceeded by any one of the by-catch species then the 5% rule should be enforced.