The objectives of the Commission as set out in Article II of the Convention are briefly discussed and the two approaches to ecosystem analysis reviewed. The top-down approach, following the flow of energy from primary production through to the animals of interest give-s a broad understanding of how the system works, and rough estimates of the potential yield at various trophic levels. It is not very useful in formulating specific management advice e.g., whether a catch of the same order of magnitude as the potential yield is too high or not. For providing advice the bottom-up approach is more useful, starting with examining the dynamics of the stocks of individual species, especially those currently being exploited.

"Ecosystem management" in the Antarctic will therefore depend on having a good understanding of the dynamics of each important species. The present knowledge of the behaviour of different stocks under exploitation, and of the basic parameters (growth, mortality, etc.) is reviewed. These range from fairly good for whales, through moderate for fish and krill, to poor or non-existent for squid. The most serious inadequacy is probably the lack of good methods of monitoring changes in krill abundance. Most catch per unit data for krill reflect local density rather than overall abundance. 

The forms of interaction between species are discussed, and related to the work of modelling and data collection. It is suggested that of the various types of models, strategic simulation models which help address the right questions are, in the current state of knowledge, the most valuable.