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 4 . Fish and Squid 



Fish and squid have had perhaps the largest potential 

 for population increases resulting from the loss of whale 

 biomass. However, they are also two of the groups about 

 which we know virtually nothing and which are unlikely to be 

 noticed changing in population size (Mackintosh, 1970) . Both 

 fish and squid may have potentially large stock sizes and an 

 important effect on cropping krill to lower levels. Unfortunately, 

 reliable data on the total biomass, distribution, and metabolic 

 rates of fish and squid are not available to demonstrate 

 conclusively the significance of these groups' krill predation. 

 If feeding and metabolic rates of squid and fish were better 

 known, it might be shown that these smaller species, many of 

 which presumably feed on krill year-round, may consume 

 tremendous volumes of krill per unit biomass annually. 



5. Discussion 



Under pristine (unharvested) conditions, the Antarctic 

 marine ecosystem was subject to continual shifts in biological 

 interactions and physical parameters such as currents, 

 nutrient upwelling, and climatic change. In response to 

 these minor oscillations within the system, the biological 

 constituents fluctuated constantly. The system is inherently 

 dynamic; relationships and abundances of populations are by 

 no means static. Manipulation of major portions of the 

 ecosystem through commercial harvest of whales and seals 

 conceivably caused greater fluctuations within the ecosystem 

 than normally occurred. Moreover, just as the ecosystem 

 would respond to minor fluctuations in the past, so would it 

 respond to major changes in the trophic balance. It is 

 difficult to doubt that following the severe reduction of 

 whales, the various other elements of the Antarctic marine 

 food web readjusted to more fully utilize krill resources 

 formerly consumed by the whales. For these reasons, arguments 

 proposing a krill "surplus" are unconvincing and fail to 

 acknowledge likely ecosystem responses. 



B. Potential Ecosystem Changes Resulting from Future Krill 

 Harvest 



Just as the Antarctic marine system reacted to commercial 

 harvesting of whales and seals in the past, so may we expect 

 future commercial harvests to cause ecological reverberations 

 throughout the ecosystem. 



1. Competition, Predation, and Ecosystem Stability 



Acknowledging that ecosystems and their biotic communities 

 are dynamic, one is faced with the difficult question of how 

 the system will respond to various perturbations. The large 



