-28- 



(Appendix D, Everson, 1977; Tetra Tech, 1978) . Because of 

 its swarming habit, E_^ superba is the predominant krill 

 species in the diets of mammals and penguins, and is the 

 only krill species of commercial importance. 



Estimates for krill standing stock vary almost tenfold, 

 from about 180 to 1350 million metric tons (Appendix E, 

 Green, 1977) . 



The circumpolar krill population may be a single breed- 

 ing stock or may be composed of several separate stocks 

 (Mackintosh, 1973; Makarov, 1974). More recent studies indi- 

 cate that the breeding area has spread geographically since 

 spawning females have been taken from the Scotia Sea, Belling- 

 shausen Sea and Bransfield Straits. Spawning occurs at the 

 surface from late November through late March. Early larvae 

 are found in the East Wind Drift, the Bransfield Strait, 

 the Scotia Sea, and the Weddell Drift (Everson, 1977; Tetra 

 Tech, 1978). The Discovery expeditions collected very few 

 eggs, and those only in the Scotia Sea (Marr, 1962). 



Krill are long lived in comparison with zooplankton in 

 warmer waters. However, there is still considerable doubt 

 about total life span and age at which sexual maturity is 

 attained. Krill may not breed until the beginning of their 

 third or fourth summer and may breed for one or two seasons 

 (Eraser, 1937; Bargmann, 1945; Ivanov, 1970; Everson, 1977) . 



Even though there is considerable scientific and commer- 

 cial interest in krill, knowledge of physiology, breeding 

 stocks, replacement rate and abundance is still incomplete. 



2. Squid 



It is possible that squid in the southern ocean are con- 

 centrated near the Antarctic Convergence (Appendix Hf BIOMASS, 

 1977). However, squid serve as food for sperm whales, seals 

 and fish whose distribution extends south toward the continent. 



No direct abundance estimates for squid or other cepha- 

 lopods are available for Antarctic waters, mainly due to 

 inadequate sampling techniques (Everson, 1977) . 



There are squid fisheries in the waters near New Zealand 

 and South America, but none in Antarctic waters. The "giant 

 squid" Mesonychoteuthis hamiltoni may be of commercial potential 

 (Everson, 1977) . 



Squid are major predators on krill. Larger individuals 

 feed on fish or other squid. 



