CCAMLR

Parameters of the Bertalanfy growth equation for 1928 and 1970–1976 were calculated on the base of summaryed data on Krill age groups singled out using method of Harding.Parameters obtained were used to calculate total Krill mortality using different methods applyed earlier only to the fish recources.
As a result of uncertainty in age groups determination were obtained wide ranging values. The most real values varied from 0.75 to 1,17.
No fishery impact on various parameters of the krill population size structure was found.

An observation program was carried out by a biologist-observer on board the krill fishing vessel More Sodruzhestva in April to August 1991 in Subareas 48.2 and 48.3. The program included observation of krill fishing operations, collection and processing of catch samples for analysing physiological status and size composition of krill and also for determining the level of by-catch of juvenile channichthyids. In general, krill density in Subarea 48.2 was twice as high as that in Subarea 48.3. Catch-per-haul was 9.51 and 4.74 tonnes respectively. Krill of two modal sizes, 45 to 48 mm and 49 to 52 mm, were dominant in catches taken in April/May in the north-west of Subarea 48.2. Krill of modal sizes 31 to 32 mm and 35 to 36 mm made up the bulk of catches in the south-east of the subarea. No by-catch of juvenile fish was observed in Subarea 48.2. Krill of the following three modal groups was dominant in Subarea 48.3: 35 to 38, 39 to 42 and 45 to 46 mm. By-catch of juvenile Champsocephalus gunnari was observed in these subareas during the period 17 to 23 May 1991. Sightings of marine mammals and birds in the vicinity of the vessel were also recorded.

Interannual variations in krill quantative characteristics in the Sodruzhestva Sea area for the period from 1988 to 1990 are discussed in this paper. It has been established, that a considerable increase in the crustacea stock in 1990 was caused by good replenishment owing to the generations of 1986 and 1987 in the conditions of their weak expatriation in 1989–1990.

The results of Butterworth et al. (1991) relating potential krill yield to a pre-exploitation survey estimate of krill biomass are extended as specified by the Third Meeting of Working Group on Krill. The most important of these extensions is integration over the ranges of uncertainty for a number of the model parameters. Results are provided for the probability of spawning biomass falling below various fractions of its median pre-exploitation level, as a function of the fraction of the biomass estimate which is set as the catch for a 20-year period. Three alternative fishing seasons are considered. Fishing in summer (near-coincident with the period of krill growth), or throughout the year, allows a greater catch (for the same risk of depletion) than in the case of fishing in winter.