In this study, we calibrated a commercial echosounder (ES70) installed on a krill fishing vessel to use it in estimating biomass of Antarctic krill (Euphausia superba). The method of calibration was to analyze the difference between the bottom backscattering strength of the commercial echosounder (i.e. ES70) and the scientific echosounder (i.e. EK60) at some transects designated by CCAMLR. 38kHz and 120kHz were used for the calibration, and krill swarm signals, obtained from multi frequencies, was examined to verify the calibration result. The analysis result confirmed the possibility of calibration by bottom backscattering strength, since the proportion of krill swarm signals within 2 dB < S_{V120kHz‒38 kHz} < 12 dB (i.e. a common ΔMVBS range of 38kHz and 120kHz to be an indicative of Antarctic krill) over the total acoustic signals were 26.95% and 92.04%, respectively before and after the calibration.

The dB-difference and characteristics of krill aggregation inhabiting Subarea 48.1, which includes the Elephant Island peripheries and the west and south of the South Shetland Islands, were estimated to distinguish Antarctic krill, using acoustics. From April 13 to 24, 2016, acoustic data were collected along 24 survey lines using the frequencies 38 and 120 kHz, and midwater trawling was performed at seven stations. Using the difference between the dB values of two volume backscattering strength (Sv) frequencies (38 and 120 kHz), a clear acoustic distinction could be made between Antarctic krill (4.9 to 12.0 dB) and fish (-4.0 to -0.2 dB). The distributions and mean Sv of krill aggregations in the Elephant Island peripheries and south of South Shetland Islands were higher than those in the west of the South Shetland Islands. The mean length/height ratio of krill aggregations in the west of the South Shetland Islands (64.5) was higher than that in the south (35.9) and the Elephant Island peripheries (33.8), with the length of the aggregations exceeding their height. It was evident that most krill aggregations were distributed between the surface layer (less than 10m) and 200m depth.

CCAMLR anticipates that acoustic data collected from krill fishing vessels will be incorporated into krill feed back management.  Acoustic data collected from fishing vessels may have different characteristics to data collected from research ships.  For example, acoustic data collected from fishing vessels may contain seabed aliased echoes and instrument cross-talk.  Analysing acoustic data on a krill-swarm, rather than the current integration grid approach, may facilitate the semi-automated processing of acoustic data and reduce post-processing time.  Using a validated aggregation detection algorithm, I estimated mean areal krill density for a small (65 km by 60 km) survey conducted in the waters off Mawson research station in the East Antarctic (66^o 25' S 63^o 14' E).  I found 61 % overlap between the variance estimates for conventional grid-based swarm-based krill density.  The processing time of the swarm-based appraoch was half that of the standard grid-based technique. Whilst additional test data sets are required, the techniques presented here can be used to further explore the efficacy of swarm-based analysis.

A dedicated krill survey for CCAMLR Division 58.4.1 during 2018/19 season is planned by Japan. No krill biomass has been estimated in the Division since 1996 when Australia carried out BROKE. There are two main objectives of our survey: (1) estimation of krill biomass to update B(0) in the area and (2) oceanographic observations in the area to detect long term changes if any. Japanese research vessel, Kaiyo-maru, will be used in the survey. The krill survey (echosounder and RMT) and subsequent biomass estimation will follow the CCAMLR standard protocol. The survey will be international oriented and participation of foreign scientists is welcome. This document is presented to SG-ASAM-17 with an intention to receive comments from the participants. Every suggestion will be duly examined and incorporated where relevant in the plan and a revised plan will be submitted to WG-EMM-17 and SG-ASAM-18 for further considerations. The final plan will be submitted to WG-EMM-18.