Fishing of the Patagonian toothfish (Dissostichus eleginoides) by the Chilean fleet (1991/92) in the Subarea 48.3 (South Georgia Island) and proposed TAC for the 1991/1993 season

This study analyses fisheries activities carried out by the Chilean longline fishery targeting the Patagonian toothfish (Dissostichus eleginoides) in CCAMLR Statistical Subarea 48.3 (South Georgia Island). From the end of December 1991 until the closing of the fishery on the 10th March 1992, the fleet caught around 80% of the TAC set for this subarea. The catch and effort data and the biological sampling carried out on board the vessels operating in the region were used for the analysis.
From the location of the hauls two separate fishing grounds could be clearly distinguished: the first one at the north of South Georgia Island, including Black and Shag rocks, and the second one at the South of the island, hauls being made at depths between 1 100 and 1 450 m. The effort applied by the Chilean fleet totalled 2.71 million hooks, 2 883 tonnes were caught at an average CPUE of 1.06 k/hook; this yield was higher to those recorded in previous seasons.
During this period the standard length of 8 340 specimens was measured at 5 cm intervals, using established sorting procedures, and also by converting the standard length to total length, where the length frequency distribution by sex was determined. The catch lengths distributions ranged between 40 and 145 cm for males and 40 and 200 cm for females. The average length was estimated at 96.7 cm for males and 108.8 cm for females. The total catch was estimated at 255 139 specimens, with a ratio of 59% males and 41% females.
The stock assessment was made by using two methodological approaches: pseudo-cohort analysis and DeLury’s method. The total catch recorded for the subarea was used, while the total effort was estimated by projecting the results of the Chilean fleet to all vessels that operated during the season. According to the biomass obtained by each method, TACs were established, using different combinations of F0.1, total length at first catch and natural mortality which were assumed to be most likely for this species. Thus, according to DeLury’s method, TACs ranged between 1 085 and 5 768 tonnes, whereas the cohort analysis gave TACs fluctuating between 7 832 and 8 210 tonnes. On the basis of these results, the proposed TAC for the 1992/93 season in Subarea 48.3 is 6 000 tonnes.