Biomass/CCAMLR krill review

Current knowledge of the ecology, biology and life history of the Antarctic krill Euphausia superba Dana is reviewed. Emphasis is placed on recent developments, particularly on the results of various national and international research programmes loosely co-ordinated under the auspices of BIOMASS (Biological Investigations of Marine Antarctic Systems and Stocks). Attention is focused on topics which are either directly or indirectly applicable to the effective management of krill exploitation within the provisions set out by Article II of the Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR).
The hydrography of the Southern Ocean is briefly reviewed and the horizontal distribution of krill on various scales ranging from the global to individual aggregations (e.g., swarms) is discussed. Factors likely to influence the distribution on all scales are discussed and the question of stock separation considered.
Recent attempts to assess the krill standing stock directly are examined, with particular emphasis being given to the First International BIOMASS Experiment (FIBEX) acoustic survey of 1981. General problems in assessing krill acoustically and by other direct methods are discussed, and some solutions proposed to the various associated problems.
A broad overview is given of recent progress in estimating krill production through studies of age and growth, energy budgets for individual animals, and predator consumption rates. Various models of interactions between krill and its major predators, including Man, are considered. It is concluded that neither the production estimates nor the models are adequate at present for setting optimum harvesting levels for krill.
Special attention is given to the phenomenon of aggregation in krill. Physical and biological characteristics of different types of aggregation, and the effect on them of environmental factors are discussed, as are various models of aggregation formation, maintenance and dispersal.
Finally, attempts are mads to consolidate current knowledge of aspects crucial to the ecosystem management approach espoused by CCAMLR. It is concluded that deficient information on Antarctic marine ecosystem components, and on interactions between them, precludes the implementation of a realistic multi-species management approach at present. The best prospect of obtaining the information needed for the future development of the required models appears to be through intensive studies in a number of relatively small, preferably biologically distinct, areas.