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Krill are omnivores, eating other zooplankton as well as 

 phytoplankton. Krill are usually considered to be about 

 half of the zooplankton population (Gulland, 1970) . Other 

 zooplankton include copepods, araphipods , and chaetognaths 

 (Hopkins, 1971) . Krill play a crucial role in the Antarctic 

 marine food web because of their great abundance and because 

 they are the main prey item for most of the predators in the 

 ecosystem. 



Squid are probably abundant in the Antarctic (Appendix 

 F. BIOMASS, 1977). Squid eat krill and fish. Many fish 

 eat krill. Birds, predominatly Adelie penguins, also eat 

 krill (Prevost, in press) . Other Antarctic birds include 

 other penguins, petrels, albatrosses, and skuas. 



Crabeater seals, a krill eating species, are the most 

 abundant of Antarctic seals. Leopard, Ross, Weddell, 

 elephant and fur seals are also present. The baleen whales 

 which migrate into the Antarctic, fin, blue, sei, humpback, 

 and minke whales, feed extensively on krill. Southern right 

 whales are occasionally found south of the Convergence. The 

 toothed whales, sperm and killer whales and some small ceta- 

 ceans, are probably resident throughout the year. 



Common and scientific names for species discussed in 

 describing the Antarctic marine ecosystem are listed in 

 Table 1. 



At the present state of biological knowledge, standing 

 stocks of resource populations other than whales in Antarctic 

 waters are not well known. Abundance estimates for seals 

 and penguins still vary considerably among investigators. 

 The overall abundance of fish and cephalopods is virtually 

 unknown. Abundance estimates and educated guesses on stock 

 sizes for potential resource populations are discussed in 

 Appendices E, F, G and H. 



1. Krill 



Krill have a circumpolar distribution, but are most abun- 

 dant in the Weddell Sea, the East Wind Drift, the Weddell 

 Drift and the South Georgia region (Nemoto, 1968; Marr, 1962; 

 Mackintosh, 1973) . Krill are found both under ice and in 

 open waters. 



E. superba collect in large amorphous swarms varying 

 from a few to several hundred meters across. Swarms are ap- 

 parently composed of individuals of a single age class. 

 Swarms occur at varying depths from the water surface down to 

 about 100 m. Not all krill are found in swarms. Even in 

 regions of greatest abundance krill distribution is patchy 



