The diet composition and feeding intensity of mackerel ice fish (Champsocephalus gunnari) around South Georgia in January/February 1991 was analyzed in 3877 stomachs collected on 44 stations. Both, the proportion of krill (Euphausia superba) in the stomachs and the feeding intensity were uncommonly low in a period when energy-rich food is needed for the final maturation of the gonads.
Abstract:
An adaptive approach was used to assess the Champsocephalus. gunnari stock in Area 48.3. Values of catch/effort by age group and by year of fishing were used in conjunction with abundance indices from trawl surveys in tuning the VPA.
The C. gunnari stock at the start of the 1990/91 season is estimated at 184 thousand tonnes.
Calculation of TAC was carded out keeping in mind the change to the fishing regime brought about by a change in mesh size (90 mm).
A TAC of 59.4 thousand tonnes for C. gunnari is advised for an optimal regime of fishing operations at a level of F0.1 = 0.65.
Abstract:
An adaptive approach was used to assess the Notothenia gibberifrons stock in Area 48.3. It is demonstrated that when tuning the VPA using abundance indices from trawl surveys it is imperative to estimate the catchability coefficient. This parameter was equal to 0.326 to 0.635.
An adaptive approach in this case involved using a target function in the form of the sum of square deviations in logarithms of observed and calculated biomass indices and resulted in an estimate of from 21.5 to 42.1 thousand tonnes for N. gibberifrons biomass in the 1989/90 season. It is thus possible to suggest a TAC of 1.9 to 2.7 thousand tonnes.
A similar approach is recommended for assessing the stock of other commercial species in this area.
