Seasonal variation in acoustic estimates of krill density at South Georgia during 2001/2002

Four separate acoustic surveys of Antarctic krill (Euphausia superba) were conducted around South Georgia in the 2001/2002 season: one in November 2001 (early); two during January 2002 (middle), and one in May 2002 (late). The surveys were the second in a five-year series of observations designed to complement and extend an existing time series of summer surveys maintained by the British Antarctic Survey regularly since 1996. Krill density in November was low (5 g m-2), higher in both the two surveys in January (46g m-2 and 72 g m-2 ) and had decreased to 12 g m-2 by May. Our repeated surveys at South Georgia have revealed a similar pattern of change to that observed in 2000/2001 and highlight the importance of understanding the relative contributions of physical and biological processes to krill population dynamics in the region.