CCAMLR

Longline fishing for Patagonian toothfish Dissostichus eleginoides in the South African Exclusive Economic Zone around the Prince Edward Islands commenced in 1996. This paper summarises seabird bycatch during the year July 1997-June 1998. Data on seabird bycatches were obtained from fishery observers aboard all 11 sanctioned fishing trips, representing a fishing effort of 4.3 million hooks. This is 13% more than the number of hooks reported set in 1996-97, but total effort probably declined during 1997-98 as a result of a decrease in the number of unsanctioned vessels operating in the area. Observers reported 498 birds of five species killed. White-chinned Petrels Procellaria aequinoctialis predominated (96%), followed by giant petrels Macronectes spp. (3%), with Yellow-nosed Mollymawks Thalassarche chlororhynchos and crested penguins Eudyptes spp. each contributing Most birds were killed during setting. There was considerable variance between vessels (range among trips 0.000 to 0.456 birds per 1 000 hooks), with

Studies on DNA microsatellites and a tagging programme both provide information on the degree of interchange of Dissostichus eleginoides (Patagonian Toothfish) between two sites 40 nautical miles apart near Macquarie Island. Five DNA microsatellite loci were identified that showed polymorphism levels appropriate for population structure analysis, and two of these gave results that suggest samples from the two sites are not homogeneous at the 5% probability level. While the other three loci did not demonstrate significant spatial heterogeneity, combined results across all five loci again indicated heterogeneity at the 5% probability level. Results from tagging experiments support the inference from the genetic analyses that interchange of fish between the two sites is very low. Of 469 recaptures at both sites combined, only one fish had moved between sites. As the DNA analysis has so far only been performed on small numbers of fish and loci these results must be regarded as preliminary, but if confirmed by further study the implication of very localised stocks of D. eleginoides will have a great effect on the management of commercial fisheries for this species.

Results of published studies on the biology, biomass and distribution of the Antarctic toothfish (Dissostichus mawsoni) were reviewed. The review focused on those aspect of the species which are of importance for the assessment of its biomass and identification of its stocks. The trophodynamics of D. mawsoni are mentioned only in brief. Most published materials refer to studies conducted in the 1970-1980s. References in current publications on new studies of this species are scarce. A list of references is appended.

Various elements of the Generalized Linear Model (GLM) used to standardise toothfish CPUE in Subarea 48.3 are investigated. Problems with crossover between the essentially summer fishery of 1992-1993 prosecuted by Russian vessels and the winter fishery of 1995 onwards prosecuted by other nationalities, coupled with the existence of the experimental fishery in 1994, lead us to suggest that future analyses should be restricted to GLMs based on winter data alone. Unfortunately, this does result in there being no data for 1993, one of the most successful summer seasons. The relationship between CPUE and depth is also explored, and tins leads to some suggestions about the distribution of toothfish of different sizes on the shelf slope. A winter GLM is described which includes a depth factor, and is used in a discussion of the recent declines in CPUE seen in Subarea 48.3.