Some aspects of feeding in the Antarctic krill, Euphausia superba

The interaction between feeding activity, swarming behaviour and vertical migration in Antarctic krill, Euphausia superba Dana, was examined by a combination of laboratory physiology studies and intensive field sampling of a patch of krill located NE of South Georgia, in April 1980. The combined use of echolocation and a series of timed net hauls from discrete depth horizons revealed a diurnal rhythm of swarming behaviour, vertical migration and gut fullness. Laboratory physiological data showed that krill will filter feed throughout the 24 h but with peak activity by night, and that filtration rate is affected by krill density. Biochemical studies in vitro indicated that rates of lipid synthesis are generally highest at the surface and by night. These results are discussed in relation to other studies of krill feeding activity and suggestions made for further research.