CCAMLR

Sea ice is a major constraint of fishery performance in the Southern Ocean seasonal sea ice zone. We use sea ice concentration data from 2002-2017 that cover the wider Weddell Sea to establish statistical models of (i) accessibility, i.e. the probability that a particular area is navigable by fishery vessels at a given time, and of (ii) repeated accessibility, i.e. the probability that a particular area is navigable by fishery vessels at a given time and again within the following two years, as requested by CCAMLR research fishery regulations. Our findings indicate that under the actual sea ice conditions almost 50% of the entire WSMPA Planning Area is not suitable for fishery vessels at any time of the year, while there are high spatiotemporal variability in repeated accessibility in particular areas such as along the ice shelf of the eastern and south-eastern Weddell Sea. We consider our models to constitute valuable, riskreducing planning tools in the further development of fishery research as well as of ship-bound tourism in the wider Weddell Sea area.

The one nautical mile integrated Nautical Area Scattering Coefficient (NASC) values of four surveys in 48.1 fishing area were calculated using both the swarm-based and conventional grid-based acoustic data processing methods. All parameter settings were consistent with the reports of SG-ASAM-2017 except that the dB difference window of Sv_{120 kHz}-Sv_38kHz is set 0 to 20 dB. And the two groups of results were compared by correlation, linear regression analysis and nonparametric significant difference tests (Kruskal-Wallis tests) to examine the validation of the developed swarm-based method for Antarctic krill density estimation. The comparisons suggest that the calculated NASC values of swarm-based and grid-based method show non-significant difference and significant linear relationship for all the four surveys. Therefore, it is concluded that the krill density estimated by swarm-based and grid-based method could be of good agreement.

During the meeting, the subgroup suggested further analysis on swam-based approach and grid-based approach based on data in the paper. In accordance to the suggestions, further analyses were undertaken and the results were shown in Appendix A.

The distribution and abundance of krill aggregation inhabiting the Subarea 48.1, which includes the Elephant Island peripheries and the west and south of the South Shetland Island, were estimated using an acoustics survey. Acoustic data were collected with 38 and 120 kHz from April 13 to 24 in 2016 and 38 and 200 kHz from March 6 to 14 and 38 and 120 kHz on April 27 and May 5 in 2017. Krill were collected by the commercial middle trawl fishing vessel. The data were processed and analyzed following CCAMLR standard protocols using swarm integration (SHAPES module within that software for swarm identification) based on data from a transect-based survey. The weighted krill density and biomass were estimated to be 0.20 g/m² and 18 thousand tons (CV=33.8%) applying S_v difference 3.96-5.91 dB and 0.92 g/m² and 83 thousand tonnes (CV=31.4%) applying S_v difference -3.0-13.8 dB in 2017, respectively. Krill density and biomass were significantly higher in 2016 than those in 2017.

Hydroacoustic data were collected to study the distribution and abundance of Antarctic krill relative to their predators in the Southern Ocean during annual logistic summer trips and dedicated research winter trips to Antarctica on board the South African RV SA Agulhas II. The 38, 120 and 200 kHz transducers mounted on the drop keel of the research vessel were used to collect acoustic data; where the first year (2014) of the study logged acoustic data during daytime only whilst surveys in later years (2015-2016) logged data all day long. Target sampling was conducted using the Methot ichthyoplankton net, zooplankton nets and buckets. Preliminary results from those surveys are summarised herein. Collections of acoustic data from dedicated and opportunistic surveys for this work indicate that the RV SA Agulhas II can be effectively utilised for acoustic research. Furthermore, this vessel provides allowance for other essential concurrent research including oceanographic sampling and top predator observations.

The objective for the Multinational Large-Scale Krill Synoptic Survey in CCAMLR area 48 in 2019 is to provide an updated estimate of the biomass of Antarctic krill (Euphausia superba) used in models to estimate sustainable yield. The planned survey follows, as close as possible, the design of the CCAMLR 2000 survey, that was undertaken in the year 2000. The basis for comparisons will depend on the degree of coverage and methodology and equipment available. The survey will involve the collaborative efforts of Norway, Association of Responsible Krill fishing companies (ARK: companies from Norway, Korea, China and Chile), United Kingdom, Ukraine, Korea and China, and hopefully also other nations that still needs to confirm their participation.

The current survey plan organization is presented for consideration by SG-ASAM. Norway has volunteered to co-ordinate the survey with other members dedicating personnel to specific tasks. It is requested that members who has already made commitments on ship time, also allocate contact personnel as proposed.

This paper has been developed after a wider consultation extending beyond the authors list. It discusses some specific organizational and technical challenges to be considered by SG-ASAM. We request advice from ASAM on “minimum requirements” regarding acoustic instrumentation and sampling gear to achieve approximate consistency with the CCAMLR B0 data collection protocol.

To investigate the utility of broadband sound for Antarctic krill acoustic surveys, we will conduct echo sampling with a scientific broadband echosounder EK80 (Simrad-Kongsberg) during a dedicated krill survey for CCAMLR Division 58.4.1 during 2018/19 season by Japanese research vessel, Kaiyo-maru. The echo sampling will be performed during targeted RMT1+8 tows. Spectra of volume backscattering strengths will be obtained from the sampled echoes and their characteristics will be investigated. Further, orientation and length distributions will be inferred from the measured spectra with theoretical acoustic scattering models. The survey and analysis plans are presented in this paper.