Areal cover is calculated for the Statistical Sub-areas (48.1, 48.2 and 48.3) from which the bulk of the commercial krill catch has been taken. Correspondingly, the areas of the following four regions are also calculated - (a) the CCAMLR Convention Area, (b) south of 55°S, (c) containing krill concentrations and (d) south of the mean summer position of the 0°C isotherm using specialised computer software based on a Lambert Geographical Projection. As a secondary step, the mean krill density estimate for the West Atlantic during FIBEX (First International BIOMASS Experiment) is expanded to give a global biomass for krill within each of the above four regions. Similarly, the maximum estimated krill density for the West Atlantic during FIBEX is used to obtain an upper limit for the biomass of krill in the three Statistical Sub-areas being considered. The implications of the results is that the impact being made by the current krill fishery on the krill resource in Sub-areas 48.1, 48.2 and 48.3 merits discussion.
Abstract:
Finfish have been harvested in the Atlantic sector of the Southern Ocean since the end of the 1960s mainly by the Soviet Union. Notothenia rossii marmorata ,vas the target species in the first peak years 1969-71 which yielded about 500,000 tonnes in 2 seasons around South Georgia. Since 1975/76 fishing has been mostly directed to the icefish Champsocephalus gunnari. and to a lesser extent Patagonotothen brevicauda guntheri. Catches of C. gunnari were highest at about 240,000, 220,000 and 100,000 tonnes in 1976/77-1977/78, 1982/83-1983/84 and 1986/87-1987/88.
N. rossii marmorata is the species most adversely affected by the fishery. The present stock size around South Georgia is less than 5 % of the level before the fishery started. Recruitment has fallen since the second half of the 1970s. At the present level of recruitment, simulation studies indicate that the stock size will recover slowly, only doubling over a period of 10 years.
Stock size of C. gunnari around South Georgia is largely dependent on the strength of the recruiting yearclass which also forms the bulk of catches in the fishery. Stocks of C. gunnari around the South Orkney Islands and in the Antarctic Peninsula region seem to be heavily depleted by fishing and are in need of conservation measures.
P. br. guntheri is the only species in the fishery which was unregulated until 1988/89. Stock assessment is largely influenced by uncertainties in the determination of the natural mortality. At high levels of M (0.8-0.9) stock size as well as recruitment indicate a downward trend.
