CCAMLR

The parameters used to model gear selectivity and maturity at length in the SKDM were derived from data available at the CCAMLR Data Centre or in documents submitted to past meetings of the Scientific Committee. In the SKDM, if l50 for selectivity and maturity is to be sampled from a uniform distribution, and applied to a standard function width, then these should be
lr50 = U[30,39] wr = 9mm for gear selectivity
Im50 = U[32,37] wm = 6mm for maturity

Ten hauling for Dissostichus eleginoides were performed from the 11lth to the 21 of April 1994, wich were related between them, when they contact within a circle of 10 nm of diameter, whose center was at 55° 03’ S 36° 53’ W. Leslie Method was applied to the data. initial biomass was projected to 3244.8 nm2, obtaining an estimated biomass of 937.8 ton. Due to statistical limitations of these data, another analisis based in the density (Kg/nm2) on the fished area was used. The positions given by the vessel were confirmed with information obtained from an automatic position system (ARGOS).

A total of 63 hauls and 10 oceanographical legs were obtained. Of these, 44 hauls taken in Subarea 48.3 on a random stratified des n are used to estimate the standing stocks of the main commercial fish species along different methods, as well as their length frequency distributions. A change in surface water temperature of about -0.5 to -1.0 in a period of approximately 20 days was detected around South Georgia Islands. In the Scotia Sea the boundary of the Weddell-Scotia confluence was found within historical limits while surface water (down to 50/70 meters) was warmer than expected. It was also found that the spatial structure of fish populations significantly affects the results of biomass estimates.

A preliminary histological analysis on the ovarian development in Champsocephalus gunnari was carried out. Six stages of oocytary development were identified and are similar to those described for other species. A gonad maturation scale was elaborated and adapted to the macroscopic scale commonly used. Oocytary resorption processes were observed during ovarian maturation. In some cases the ovaries presented few atretic oocytes ; in others a generalized regression was found. In the southwest portion of the South Georgia shelf, 50 % of the ovaries exhibited a pre-reproductive regression stage similar to that reported for the same species in the 1991 summer season.

The diet composition of the icefish Champsocephalus gunnari caught in the Subarea 48.3 in February/March 1994 was analyzed using the frequency of occurrence (%) method. Krill (Euphausia superba) followed by the amphipod hyperiid Themisto gaudichaudii were the main prey items at South Georgia and Shag Rocks; fish were found in the stomachs more frequently than in past seasons around South Georgia, in parallel with the virtual absence of mysids and Thysanoessa spp.. Krill was available for fish in common levels, equivalent to those of previous years (e.g. 1985, 1992). However, high proportions of empty stomachs were found at South Georgia and Shag Rocks, close to the values reported for the 1991 year of krill "shortage". Besides, the tentative analysis of part of the samples using the coefficient Q (%) showed a greater importance of T. gaudichaudii with respect to krill. It is possible that the inconsistencies found between the results obtained by both methods are due to a particular spatial distribution of krill in the area in the period of study, but no previous data are available for comparison. No krill aggregations were found in the region by acoustic methods in the 1994 summer season; a fact that might be related with a significant change in surface temperature observed during the cruise.