Estimating Antarctic krill density from multi-beam observations using distance sampling methods

The Scientific Committee has requested SG-ASAM to provide advice on the collection and processing of acoustic data from fishing vessels.  Some krill fishing vessels are equipped with scanning or multi-beam sonars.  Here I highlight a recently published analysis technique - an adaptation of distance sampling theory - that provides a general means for estimating krill density and biomass from vertically oriented multi-beam echo-sounder data.  I describe an extension to this approach that may, subject to the constraints of krill target strength models, acoustic instrument stability, and survey design allow the use of data observed with horizontally oriented multi-beam and scanning sonars to contribute to krill abundance estimation.