Acoustic estimation of krill abundance utilizing volume scattering measurements

More than two decades of intensive ecological research in the Antarctic have refined the oversimplistic view of "the Antarctic ecosystem" towards identification and investigation of a number of different subsystems. Within the pack-ice zone of the Weddell Sea (Atlantic sector of the Antarctic Ocean), a summer pelagic system breaks up into ice-bound and deep-living systems in winter. Furthermore, an export system at the borders of the Weddell gyre can be distinguished from a retention system at its center in summer. Continued studies allow for simple energy-flow budgets to be constructed of some of these subsystems, in which the varying role of krill can be analyzed. Such a model is presented for the ecosystem on the eastern Weddell Sea shelf. Although the benthic components dominate this ecosystem by biomass, the major part of the flows takes place in the pelagic, and these flows are analysed with focus on krill. The results are subsequently compared with a preliminary trophic flow model of a temperate shelf ecosystem off the southern coast of British Columbia. Krill appear to be generally wellused, being of more importance as food for homoiotherms in the Antarctic, and to fish off British Columbia. In view of efforts towards changing the exploitation of krill in any of these ecosystems, the role of krill in the food web needs to be quantified better than to date. After a brief introduction to the modeling approach used. the role of krill in this high Antarctic ecosystem will be compared to its importance in a temperate shelf ecosystem. based on a preliminary trophic flow budget of the shelf off British Columbia.