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Nemoto (1966), Mauchline and Fisher (1969), Mackintosh (1970, 

 1972b, 1973, 1974), Ivanov (1970), and Everson (1976). 

 Everson's (1977) excellent review of living resources in the 

 Southern Ocean summarizes much of the information on krill and 

 is heavily drawn upon in the following discussion. 



1. Distribution 



Krill are found in a circumpolar band around Antarctica and 

 are thought to be swept generally northward by surface currents 

 (Baker, 1954; Marr, 1962; Mackintosh, 1973; Everson, 1976) 

 (Figure 5) . Although several species of the genus Euphausia 

 exist south of the Antarctic Convergence, Euphausia superba 

 dominates. Figure 6, illustrating the relative distribution of 

 Euphausiid and vertebrate species on a north/south latitudinal 

 gradient, shows that Euphausia superba has a wide distributional 

 range south of the Convergence. Although krill have a circum- 

 polar distribution, there are areas of variable densities. 

 Traditional areas of high krill concentrations include the East 

 Wind Drift, the Scotia Sea, and South Georgia area (Beklemishev, 

 1960, 1961; Marr, 1962; Nemoto, 1968; Mackintosh, 1973). 

 Brinton (1976) suggested that two major factors, current eddys 

 and nutrient upwelling a different locations around Antarctica, 

 contribute to the large scale distribution patterns of krill. 

 Voronina (1966b) stated that in addition to the effects of 

 currents, large krill concentrations may be due to prespawning 

 accumulations . 



Everson (1977) discusses various theories about krill 

 distribution and movements. Perhaps the two main hypotheses 

 about krill distribution are that 1) krill populations for the 

 most part stay in one spot and 2) krill are distributed in a 

 large circulation pattern. Some authors feel that krill remain 

 in the same general area throughout their life, and that this 

 might be accomplished by swimming in the opposite direction of 

 currents and drift (Marr, 1962; Semenov, 1969; Mackintosh, 1972b). 

 Although krill appear able to swim against currents up to speeds of 

 .33 knots, resisting currents for sustained periods seems 

 energetically unfeasible. Krill might also stay in one area by 

 migrating through different water layers with opposing currents 

 (Chevtsov and Makarov, 1969) . Krill could ride the currents in 

 one direction, and then, by making a relatively short vertical 

 migration, enter the adjacent water mass and be carried back 

 towards the starting point. Physical barriers, caused either by 

 a temperature gradient or currents due to upwelling patterns, 

 might also limit krill distribution to one area (Khvatskiy, 

 1972; Makarov, 1972; Fisher, 1976). 



Ruud (1932) felt that krill may be swept over wide distances 

 by major circulation patterns, and the Weddell Sea gyre with its 

 associated high krill concentrations is offered as an example of 



