Raw and calibrated NASC from repeat acoustic transects sampled by commercial fishing vessels is one approach to collecting data to inform within season feedback management schemes. However, a lack of sufficient data exists from which to examine its efficacy. In addition to the time/monetary commitment by fishing nations to collect such data, a time series of data, like that collected by the U.S. AMLR Program in Sub-area 48.1, can provide background information to help develop these feedback approaches. In this paper I present some basic information from data collected by the U.S. AMLR Program along repeat transects sampled twice during summer between 1996 and 2011.  These data will be available during the SG-ASAM Meeting for investigation of potential utility in formulating plans for development feedback management strategies.

In 2010, CCAMLR tasked the Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) to recalculate the catch limit for Antarctic krill in the Scotia Sea based on updated acoustic algorithms developed since the first calculation in 2000. Subsequent to the 2010 SG-ASAM, code used to obtain biomass (B₀; tonnes) estimates was compiled and provided to the Secretariat for reference and use by others to derive biomass estimates. Over the last several years, attempts by many nations to use this collection of code has revealed inconsistencies and omissions in the documentation, complicating attempts by interested parties in using this approach to estimate biomass in other areas. Here we present new, more efficient, thoroughly documented, and generically applicable code for calculating acoustic biomass estimates for any area based on the CCAMLR 2000 survey methods. Using data from the South Orkney Island stratum during the CCAMLR 2000 survey, results from the new code are compared to the original and shown to be comparable. In 2010, CCAMLR tasked the Subgroup on Acoustic Survey and Analysis Methods (SG-ASAM) to recalculate the catch limit for Antarctic krill in the Scotia Sea based on updated acoustic algorithms developed since the first calculation in 2000. Subsequent to the 2010 SG-ASAM, code used to obtain biomass (B₀; tonnes) estimates was compiled and provided to the Secretariat for reference and use by others to derive biomass estimates. Over the last several years, attempts by many nations to use this collection of code has revealed inconsistencies and omissions in the documentation, complicating attempts by interested parties in using this approach to estimate biomass in other areas. Here we present new, more efficient, thoroughly documented, and generically applicable code for calculating acoustic biomass estimates for any area based on the CCAMLR 2000 survey methods. Using data from the South Orkney Island stratum during the CCAMLR 2000 survey, results from the new code are compared to the original and shown to be comparable. 

This paper is intended to provide a generalised example of a procedure for krill density estimation, based on a worked example from the Balleny Islands (WG-EMM-15/17).  Explicitly, this paper is not the CCAMLR krill density estimation procedure, but has been written as a discussion document for the 2016 SG-ASAM meeting.