2007 krill biomass update of the South Shetland and Elephant Island regions of Area 48

Antarctic krill biomass trends in the South Shetland Island region of Area 48 are presented. Updated time series using the Stochastic Distorted Wave Born Approximation, and a dynamic ?Sv krill delineation model are used to derive krill biomass. This paper provides updated (through summer 2007), acoustic biomass estimates previously presented at the 2006 WG-EMM meeting in Namibia (WG-EMM-06/32). In 2007, biomass in the South Shetland Islands region exceeded 19 million tons. This increase from <500 000 tons in 2006 represents the largest biomass recorded in nearly 20 years and a 50% increase over the peak observed in 2003. Biomass was comprised of 1, 2 and 3+ year old krill, suggesting either a large recruitment event was not captured in surveys conducted in 2006 or 2005, or that advection from elsewhere is responsible for the recent increase.