c-iv 



The ecological role of krill is unique. Krill have a 

 longer life span than other marine zooplankton, requiring 

 several years to reach sexual maturity. One species pre- 

 dominantly, E. superb a , supports many different predators in 

 five major groups, fish, squid, birds, seals, and whales. 



The dependence of many predators on krill as the main 

 food resource implies that overexploitation of krill will be 

 very damaging to most other populations within the ecosystem 

 as well. If krill populations are reduced to the same ex- 

 tent that whale populations have been, then the other poten- 

 tially harvestable resources will also become scarce. Be- 

 cause krill have a central place in the Antarctic marine 

 food web, excessive harvesting would be dangerous to the 

 entire system. 



The reliability of data on standing stocks of various 

 Antarctic populations varies. The extremes of the food 

 chain, mammals and plants, are the best known. Primary 

 production averages about 25 gC/m^/year or 9500 x 10° metric 

 tons wet weight of plants produced annually. This produc- 

 tivity estimate is consistent with krill standing stock of 

 200 - 600 X 10° tons and an annual krill production of 350 - 

 400 X 10° tons. Krill population estimates are not based on 

 direct sampling data, but instead are inferred from esti- 

 mated predation on krill. Good quantitative estimates of 

 krill abundance are not available, in spite of great 

 scientific and commercial interest, but are needed. 



Direct estimates of fish and squid stocks are not 

 available. Again population estimates are inferred from, 

 predation estimates, and are not reliable figures. The 

 estimates of 14 x 10^ tons for fish and 12 x 106 tons for 

 squid in this report are speculative. Squid are probably 

 underestimated . 



A standing stock of 0.27 x 10° tons of birds, mostly 

 Adelie penguins, is a good estimate for Antarctic waters. 

 Estimated populations of 5-5 x 10° tons of crabeater seals 

 (25 million individuals) and 1.1 x 10° tons for all other 

 seals combined are reliable. Estimated whale stocks derive 

 from fishing data and are very reliable. Current stock 

 estimates for whales are 4 x 106 tons fin, 1.4 x 10° tons 

 minke, 0.8 x 10° tons blue, 0.7 x 10° tons sei, 0.08 x 10° 

 tons humpback, and 1.16 x 10° tons sperm whales. 



Estimated annual predation on krill amounts to some 

 330 X 10 tons. Crabeater seals account for over 100 x 10° 

 tons of the total. Squid may consume almost as much. 

 Present baleen whales stocks take only about 43 x 10° tons. 



A commercial harvest of krill would compete with 

 predators. Krill harvested will come from the 330 x 10° 



