Acoustic Characterization of Swarms of Antarctic Krill (Euphausia Superba) From Elephant Island and Bransfield Strait

Abstract

Time series of acoustic observations with three frequencies were made on Antarctic krill (Euphausia superba) near Elephant Island and in Bransfield Strait. Local changes of biomass were ten-fold over 2-3 days. The total biomass in a very large swarm near Elephant Island was 2.1 million metric tons distributed over 450 km2. The abundance in the swarm was 200–-500 g/m3 over a vertical extent from 10-240 m. Smaller patches were 40-150 g/m3 and often associated with the 100-150 m bottom contour. Assessing the distribution and abundance of very large swarms presents problems beyond those of routine acoustic surveys.