CCAMLR

An analysis of the Patagonian toothfish (Dissostichus eleginoides) fishery was carried out using data obtained during the 28th cruise of the SRTM Primorets to the Kerguelen Islands economic zone in the 1994-1995 season.

New catch data reported to CCAMLR indicate that Notothenia rossii was heavily exploited in Subarea 48.3 from 1966- 197 1, rather than just 1970 and 197 1 as previously reported. Previous assessments, based on the incomplete data set, had indicated a 1970 biomass of 600 000 tonnes and an unrealistic stock history considering that this stock was the first to be exploited in the Antarctic. A VPA using the new data suggests that unexploited biomass was over 900 000 tonnes, and declined in a manner to be expected from a new fishery. However, on the basis of historical reports and analyses of stock histories, it is suggested that 50% of the catch of 400 000 tonnes reported from 1970 was Champsocephalus gunnari, rather than N. rossii, and that 25% of the catch in 1969 was also C. gunnari. A VPA run with these catches predicts a more reasonable stock history for a species undergoing first exploitation, and an unexploited biomass of 600 000 tonnes prior to 1966.

In order to avoid several problems associated with assessing the D. eleginoides stock in Subarea 48.3, it has been proposed to use the FAO programme ANACO (Mesnil, 1989) which allows one to make coefficients of fishing mortality F more precise by using catch data on age groups without resorting to additional information on effort. VPBAS files for running the programme were created using our data as well as CCAMLR data. Some assumptions were made for this exercise. Assessments for the period 1984 to 1994 revealed that at a level of M = 14, the mean value of F is 0.148, while the toothfish spawning stock for 1989 to 1994 is between 17 and 29 thousand tonnes. The author believes that the ANACO cohort analysis programme has significant potential for further improving both stock assessments and calculations of F by adjusting the catch database and using variable parameters of natural mortality and mean fish weight.

Ichthyoplankton samples were obtained during the Italian Antarctic Oceanographic Cruise carried out in the western Ross Sea in November-December 1994. The present study focused on improvement of the knowledge of the larval fish community in relation to its distribution and relative abundance. A midwater trawl (Hamburg Plankton Net) was used to collect samples at 26 stations. Larval and juvenile specimens of twentyone species belonging to six families (Artedidraconidae, Bathydraconidae, Channichthyidae, Macrouridae, Nototheniidae and Paralepididae) were collected from surface to 380 m depth. Mean relative abundance of larval fish in the whole area was about 2.7 specimens / 1000 m3 of sea water filtered. The upper 100 m of the water column showed the greatest species diversity and abundance. Postlarvae and juveniles of Pleuragramma antarcticum were the most abundant, followed by larval and postlarval specimens of Chionodraco sp. It was noteworthy the high number of Trematomus lepidorhinus (570 larvae) found in a single station off Terra Nova Bay. Our data give evidence of a great species diversity of the larval fish community in the western Ross Sea and show a greater abundance of fish larvae in inshore than in offshore waters.