-33- 



If krill should be so depleted that some other group, 

 such as copepods , became the most abundant zooplankton, a 

 difference in overall food web structure for the ecosystem 

 could result. Since copepod populations are dispersed, they 

 would not support the same kind of large predators which 

 krill can support by swarming. A hypothetical copepod- 

 myctophid food chain might contain the same amount of carbon 

 as the krill food web does now, but much more dispersed, 

 so that the resources would not be as readily available, 

 either to large predators or to commercial harvesting, as 

 they are in the present system. 



Crabeater seals are the biggest consumer of krill, taking 

 about 106 million metric tons annually. Squid may take 100 

 million tons and fish 60 million tons although those esti- 

 mates are not reliable, since fish and squid abundance esti- 

 mates are speculative. Baleen whales consume about 43 million 

 tons annually at present, birds about 14 million tons, and 

 other seals about 3 million tons. Estimated annual total 

 predation on krill is about 340 million tons. Krill harvested 

 will come from the total now consumed by predators, not from 

 some hypothetical part of the stock which is not utilized by 

 predators (Appendix E, Green, 1977) . 



At initial stock levels, baleen whales consumed about 

 150 million tons more krill than do present populations 

 (Laws, 1977a). The amount of krill consumed by seals, birds, 

 fish, and squid a century ago is unknown. There is evidence 

 that penguin and seal populations have increased in .response 

 to increasing krill availability as baleen whale populations 

 decreased (Conroy, 1975; Laws, 1977b) . From an ecological 

 standpoint it is reasonable to expect that the Antarctic 

 marine ecosystem has adjusted to the changing whale populations, 

 even though the adjustment may not yet have been completed. 

 It is also reasonable to expect that other populations in the 

 ecosystem will respond to changes in krill availability as 

 harvest levels increase. 



D. Areas of Special Biological Importance 



The Scotia Sea is one of the regions of greatest krill 

 abundance. Some fish species distributions are limited to 

 the island groups of the Scotia Arc, Kerguelens, Crozet, 

 Bouvet, South Georgia, the South Orkneys and the Antarctic 

 peninsula. 



Areas of feeding and breeding for fish, birds, and mammals 

 should be considered for protected areas as should migratory 

 pathways for whales and other migratory populations. 



