A RE-ANALYSIS AND UPDATE OF THE ANTARCTIC KRILL BIOMASS IN THE SOUTH SHETLAND ISLANDS, THROUGH 2011

Acoustically based estimates of Antarctic krill (Euphausia superba) biomass, and net-based estimates of krill density and recruitment are recalculated for the years 1996 through 2011. Recent changes in the acoustic methodology and target strength models are the basis for the recalculation. The time series of acoustic biomass indicate that krill have varied by more than an order of magnitude over this time period. Current estimates for the South Shetland Islands region are 3.6, 1.9 and 1.35 million tons for the Elephant Island, West and South Areas, during leg 1. Recruitment estimated from net based data show that 2011 was a year of good recruitment, following two years of low recruitment. Krill biomass in the northern Gerlache Strait, an area of just over 1100 km2, exceeded 110 g m-2 which results in a biomass of more than 128 000 tons. Refining biomass estimates and estimates of recruitment will help to better inform CCAMLR about the status and trends of krill in Area 48.1 an area experiencing the most rapid climate change as well as population declines of major land-based predators.