Acoustic estimates of krill abundance at South Georgia, 1981–1998

Acoustic estimates of abundance of the Antarctic krill, Euphausia superba, at South Georgia are presented for periods within ten austral summers between 1981 and 1998. This time series includes some previously published estimates arising from cruises where determination of krill density was a primary objective, and estimates derived for the first time here from acoustic data collected as a subsidiary during other studies of the pelagic ecosystem at South Georgia. Krill abundance at the island fluctuated widely from year to year over this time, ranging from ?2 to ? 150 gm-2 (wet weight). The 1982, 1991 and 1994 austral summer seasons were characterised by particularly low abundances of krill. For five of the years between 1990 and 1998 it was possible to calculate separate biomass estimates for the north-eastern and north-western ends of South Georgia. In four of these years biomass was higher to the east.