Krill distribution patterns in the Atlantic sector of the Antarctic during the CCAMLR-2000 Survey

The international CCAMLR Survey 2000 was conducted to support an updated estimate of the large scale krill biomass in the South Atlantic Sector of the Antarctic. Four vessels from Japan, Russia, the UK and the USA participated in the study during which 22 parallel hydroacoustic transects as well as four small scale shelf grids were investigated. Standard net tows were carried out during midnight and midday stations. Additional samples were take by opening-closing nets for the identification of acoustic targets. Analyses on the combined data sets from the net sampling program indicate that krill distribution showed three distinct geographical clusters of size frequency distributions. Small to medium sized juvenile and subadult krill mainly occurred east of the South Orkney Islands. Adult krill predominately smaller than 50 mm mean length dominated in a band to the north of the first cluster, while the adult krill larger than 50 mm mean size was found to the north of cluster 2 , but at the same time was mostly restricted to the area west of the South Orkney Islands. Implications are discussed arising from the stock composition and distribution patterns.