Feeding of krill around South Georgia. II. Relations between feeding activity, environment and vertical distribution

Relations between a model of the feeding activ- ity of Euphausia superba, the oceanic environment and the vertical distribution of krill around South Georgia are described. Krill with full alimentary tracts occur both above and below the thermocline, over a 20-fold range of chlorophyll concentration. Changes in chlorophyll concentra- tion, temperature, salinity and nutrients which occur down the water column appear to have no effect upon the feeding activity of krill. As the energy requirements of krill can be met with known filtration rates over the range of chlorophyll concentrations encountered, this study suggests that krill adjust their filtration rate to compensate for wide changes in chlorophyll concentration and feed throughout the water col- umn. We cannot, however, exclude the possibility that krill from all depths could have fed in the cod-end of the net in the surface layer