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The position of the manipulated component in the food 

 web has an important bearing on the reactions in the ecosystem. 

 For example, maximiim sustainable yield (MSY) approaches to 

 whale management in the Southern Ocean attempted to manage 

 individual whale stocks without regard to their position and 

 role in the ecosystem as a whole. Harvesting most of the 

 Southern Ocean whale biomass removed a large block of krill 

 consiimers in upper trophic levels. Possible reactions to 

 this harvest have been discussed above. Reactions to 

 manipulating other trophic levels in the Antarctic marine 

 ecosystem (e.g., primary consumers instead of terminal 

 consumers) may well be expected to have different results 

 than those experienced with the whale harvest. Significant 

 ecosystem disruptions may occur if fundamental producers are 

 heavily exploited. 



The effects of such a disruption could be quite wide- 

 spread. In the case of krill, removing large amounts of 

 krill may increase the competition between krill consumers, 

 the extent of which must be determined to predict ultimate 

 krill harvesting impacts. In extreme over-fishing, the 

 integrity of stocks of marine mammals, birds, fish, and 

 cephalopods as well as other invertebrates might be seriously 

 threatened. 



The type of integrated, comprehensive conservation plan 

 which makes provision for rational, controlled harvesting 

 cannot be realized through a single species maximum sustainable 

 yield approach. If the Antarctic marine ecosystem is to be 

 maintained as a viable, dynamic system, an ecosystem approach 

 to the management and conservation of all Southern Ocean 

 marine life must be implemented. 



