CCAMLR

Whole otoliths and scales were used for a simultaneous age determination of juvenile Notothenia rossii marmorata specimens collected at Potter Cove, King George/25 de Mayo Island, South Shetland Islands. Results from the analysis of both structures agreed in 95.5%. Likewise, the examination of otolith cross sections of chosen specimens confirmed in all the cases the age readings obtained from the second whole sagittal otolith. First October instead of the commonly accepted 1 July, was taken as the birth date of the fish, which is discussed. The length-age range of the fish was 18-44 cm and 3-7 years respectively, which is well in accord with the known length-age distribution of juvenile specimens of the species in the fjord. Mean length data at age presented here were compared with published values for specimens of the same area. Our data are similar to the ones reported previously for fish of Admiralty Bay, King George/25 de Mayo I. The use of whole otoliths for age determination of juvenile N. rossii marmorata proved to be a reliable method. However, it might be not viable for adult specimens.

Chaenocephalus aceratus and Pseudochaenichthys georgianus have been exploited in Subarea 48.3 since 1977 but have never been fully assessed by the Working Group on Fish Stock Assessment because of a lack of reliable biological and catch data. This paper attempts to reconstruct the fishery for these two species by assuming that 75% of the ‘unidentified fish’ caught by the Soviet Union in the years 1977 to 1988 consisted of catches of C. aceratus and P. georgianus. Biological, age-length and length data from Polish research and commercial sources has been used with the new catch data in a VPA (Variable Population Analysis). The analyses show good agreement with historical biomass estimates from surveys, and indicate that the stock of C. aceratus has decreased from 18 000 tonnes to 6 000 tonnes, and that of P. georgianus from 40 000 tonnes to 10 000 tonnes, over the period of exploitation. Projections indicate that C. aceratus is unlikely to sustain a high level of catch even when it recovers, although P. georgianus may sustain a fishery of about 2 000 tonnes. The current TAC (Total Allowable Catch) (bycatch) limit of 300 tonnes would seem to be appropriate to allow recovery of both species in the near future.