In the Southern Ocean, fishing for finfish began in 1969/70 and for krill in 1972/73. The Soviet Union was the most important fishing nation, taking 80–90% of the entire catch. More than 3 million tonnes of finfish wereharvested prior to 1992/93, most of the catch coming from around South Georgia and lies Kerguelen. After 15 years of exploitation, most fish stocks were heavily depleted. The krill catch from the Southern Ocean has been 4.9 million tonnes to date. More than 90% of this catch has originated from the Atlantic sector. 50–90% is taken from the foraging range of land-based predators during the critical period of their breeding cycle when they raise their young. This creates the potential for direct competition between krill fisheries and krill-dependent predators. Potential impacts of krill and finfishing on the ecosystems of the Southern Ocean range from endangering recruitment due to the by-catch of juvenile fish in the krill fishery to incidental mortality of birds during longline operations and the entanglement of seals in fragments of discarded or lost fishing gear.
Most fish stocks had already been over-exploited before the Convention on the Conservation of Antarctic Marine Living Resources (CCAMLR) came into force in 1982. Stringent conservation measures to halt the further decline of the stocks have been implemented only since 1989. There is evidence that some fish stocks have started to recover recently. Precautionary catch limits for krill of 1.5 million tonnes for the Atlantic sector (Statistical Area 48), and of 390, 000 tonnes for Statistical Division 58. 4.2 in the Indian sector, were set in 1991 and 1992, respectively. CCAMLR has implemented a number of conservation measures to safeguard other components of the marine ecosystems from fishing. CCAMLR adopted a system of inspection in 1989/90 and a scheme of international scientific observation in 1992. It is too early to judge the efficacy of these enforcement and data-gathering programmes.
There is a growing recognition in CCAMLR of the need for preventati ve measures in circumstances of biological uncertainty. The development of multi-species management models appears to be remote at present. The way forward is likely to be a single-species model for the krill fishery, which needs to take implicit account of the demands of natural predators, particularly at small scales. If demersal fish stocks are able to recover to their maximum sustainable yield level, the fishery potential of the Southern Ocean is likely to be much larger than current catches. The fishery potential of krill and mesopelagic lanternfish is likely to exceed that of demersal fish stocks by an order of magnitude. By contrast with the 1970s and 1980s, when most fisheries were subsidized, economic considerations and market demands will be the primary determinants of the development of fishing in southern waters during the 1990s.