A programme was implemented in the 2019/20 fishing season in the Ross Sea region to tag and release skates for population size estimation and to validate the thorn ageing method for Antarctic starry skate (Amblyraja georgiana). Skate tagging is required under CM 41-01 in the 2020/21 fishing season as well. Skates that were tagged and released in the 2019/20 season on NZL, AUS, and GBR vessels were also injected with either oxytetracycline hydrochloride or strontium chloride in order to validate age marks incorporated into the caudal thorns. In 2020/21 (and future years), skates recaptured on all vessels in the Ross Sea region should be biologically sampled and a selection of caudal thorns removed and frozen, and returned to NIWA, Wellington for subsequent laboratory analysis.

Biology, ecology, and management of macrourids in the Ross Sea was last summarised for CCAMLR in 2010. Since then, the discovery of a previously cryptic species (Macrourus caml), two additional trawl surveys, and additional work on species-specific biological productivity has been progressed to better inform management options. Due to the COVID-19 pandemic causing impacts on the time available to progress the development of management advice, this paper describes the overall work plan and the topics of associated papers that are planned to be submitted to the CCAMLR Scientific Committee’s working groups. These topics include biomass estimates of macrourids on the Ross Sea slope, species identification, distribution and abundance, life history, interactions with the fishery, mechanisms to monitor macrourid status, and options for precautionary catch limits.

The second winter survey for Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea region was conducted by the FV Janas during September and October 2019. The survey followed the northern extent of sea ice from SSRU 882B through 881B. Antarctic toothfish sampled during this survey were in spent condition by the beginning of September, gonadosomatic indices were less than 5%, suggesting spawning had ended by mid-August. Eggs collected from the plankton were at the eyed-embryo stage, comparable with day 15 of D. eleginoides development. Buoyancy was similar to newly fertilised eggs indicating a near-surface distribution. Four D. mawsoni were tagged and released with Pop-off Satellite Archival Tags provided by NOAA to examine movement patterns of adults in the region. Four adult D. mawsoni released with conventional tags during commercial fishing on the Ross Sea slope were recaptured more than 2300 km away on a seamount in SSRU 882B. Species composition and density were correlated with oceanographic variables and structured by location with respect to the Pacific Antarctic ridge.

The time series of relative abundance and age structure from the Ross Sea shelf survey is an important input to the Ross Sea stock assessment, providing information about year class strength and variability. In 2020, the estimated relative biomass index of toothfish showed an increase, the highest recorded in the survey time series. Biological data and samples were collected from more than 3,000 toothfish and bycatch species. A total of 232 toothfish were tagged and released with a 91% tagging length overlap statistic. Although the catch limit of 45 t was not exceeded, the experimental stratum N could not be sampled. Otoliths collected will be aged for the upcoming stock assessment in 2021.

The 2019 stock assessment for Antarctic toothfish in the Ross Sea region estimated the precautionary yield using the CCAMLR decision rules and by  applying the total catch limit of 3140 t between north of 70° S (19%), south of 70° S (66%), and the Special Research Zone (15%)  in accordance with conservation measure 91-05 (2016) and 41-09 (2019). That stock assessment excluded data for vessels that had been previously quarantined by the Scientific Committee of CCAMLR due to data accuracy concerns. However, after the stock assessment had been completed, the Scientific Committee recommended that data from three additional vessels (Calipso, Koreiz and Simeiz 2015-2018) be quarantined pending an assessment of the implication of catch revisions from those vessels on the management advice.

Based on an analysis by Ukraine in 2020 the total DCD reported greenweight was 203 t greater than the reported C2 greenweight (12%) across Subareas 88.1, 88.2, and 48.2 from 2014–2018 for the three vessels combined. In the Ross Sea region, the difference totalled 78 t in 2014–2018 with the greatest difference occurring in 2018 (52 t).

A sensitivity model was run using the 2019 stock assessment incorporating the DCD estimated greenweight from the three vessels to revise the catch history in the assessment model. Both the MPD and MCMC estimates of initial biomass (B₀) and current biomass for models with revised catch for the three vessels in trips between 2014 and 2018 were almost identical to the 2019 base case assessment model. Therefore, the differences for these trips resulted in a negligible impact on the estimated precautionary yield.  We recommend that the Scientific Committee does not need to revise its 2019 advice for the toothfish catch limit for the 2020/21 season for the Ross Sea region.

This report summarises fishing catch and effort in the Ross Sea region (Subarea 88.1 and SSRUs 88.2A–B) together with biological characteristics of the catch of Antarctic toothfish through the 2019–20 season. The implementation of the Ross Sea region Marine Protected Area from the 1^st December 2017, has concentrated subsequent fishing on the continental slope south of 70° S, with recent effort extending into Subarea 88.2, SSRUs A and B. Data from all years are summarised with respect to the current management areas.

The scaled length distributions showed no decrease in the size of fish caught over time in any of the management areas, although there was a strong pattern of interannual variability in the area south of 70° S that was likely driven by changes in the fine scale spatial distribution of fishing effort or the influence of strong and week year classes entering the fishery. There was a small change in the ratio of males to females over time, with a gradual pattern of more males caught in all areas. The number of fish recaptured in 2019–20 was similar to the annual average number of recaptures over the past decade. A tagged fish was recaptured after 16 years at liberty, which indicates that tags can remain in the fish over long time periods.

The Amundsen Sea region toothfish fishery has been operating since 2003. Fishery catch showed a truncation of the right-hand limb of the age distribution between 2004 and 2014 with no further age data available after 2016. We recommend that further ageing of toothfish in the Amundsen Sea region be made a priority to develop annual age-length keys and age frequencies. We further recommend that catch limits in the Amundsen Sea region be calculated following the trend analysis rules developed by WG-FSA for research blocks (CAMLR-XXXVI 2017, Annex 7 paragraph 4.33).

Division 58.4.4b has been a closed area since 2002 (CM 32-02) and scientific research has been conducted with a research plan submitted under CM 24-01 since 2008 by Japan. France joined this research plan in 2015 and a joint proposal was submitted for the first time in 2016 (WG-SAM-16/06 and WG-FSA-16/33 Rev. 1) for a period of 5 years.

Compared to last year (WG-FSA-2019/64), this research plan has been updated with 2020/21 operating details especially the replacement of Japanese fishing vessel from Shinsei-maru No.3 to Shinsei-maru No.8 with same crew and fishing gears (fishing method: Trot system) and the withdrawal of the French vessel Ile Bourbon, which will not notify this year. Furthermore, milestone tables have been updated to account for the postponement of the WG-SAM due to the COVID 19 situation.

In 2009, the marine predator research community was invited to provide tracking data to the Scientific Committee for Antarctic Research’s Expert Group on Birds and Marine Mammals. Over the next decade, the Retrospective Analysis of Antarctic Tracking Data (RAATD) team collated and painstakingly quality-controlled and filtered over 4,000 tracks (3 million locations) from 17 marine predator species, studied between 1991 and 2016. This dataset, published in a recent data paper (Ropert-Coudert et al. 2020), includes contributions from more than 70 scientists from 12 National Antarctic Programs and represents the field efforts of hundreds of individuals. An important feature of the dataset is that it is freely available to everyone. The data underpinned a second paper, published in the journal Nature this year (Hindell et al. 2020), wherein the RAATD team identified ‘Areas of Ecological Significance’ in the Southern Ocean, and highlighted the relevance of these areas for management and conservation of the region.

This paper presents a brief update on recent climate change-related research that is relevant to discussion and decision making by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) and the Scientific Committee (SC-CAMLR). It complements the SCAR Antarctic Climate Change and the Environment (ACCE) Reports, initially published in 2009, and updated annually through submissions to the CEP/ATCM. It is not intended as a synthesis report, but a summary of research that is likely to be of relevance and interest to CCAMLR.