The introduction of the Ross Sea region Marine Protected Area has elevated the need for research (including fisheries research) to inform the Research and Monitoring Plan and to evaluate the effectiveness of the Marine Protected Area. All research should be based on a robust experimental design, and in particular, fisheries research within the Ross Sea region should:

1. meet a high standard of experimental design;
2. derive the maximum scientific outcomes from proposed activities; and
3. ensure that robust scientific conclusions can be drawn from the outcomes.

To meet this challenge, we provide a guide for the preparation and evaluation of fisheries research that will interact with the Ross Sea region Marine Protected Area. These include design aspects such as strata definition, catch rate standardisation, vessel calibration, station randomisation, and power analyses, as well as implementation aspects such as data collection requirements. These aspects of design are critical to ensure robust scientific conclusions concerning, for example, local area fish abundance, life history attributes, and ecosystem structure and function.

The CCAMLR Tagging Programme is a key part of CCAMLR’s management of toothfish fisheries and linking the details of recaptured fish to that of tagged fish is a key element of the programme. The CCAMLR Secretariat has developed a new tag linking approach that is designed to provide greater flexibility in linking recaptures to releases, including where a recapture is linked with equal probability to multiple releases. This new approach uses more of the available data to increase the level of transparency and provides an index of the level of confidence in all linked mark-recapture data.

The Secretariat requests advice from the Members on processes for deprecating the existing tag-linking approach and transitioning to the new routine as the default tag linking method used by the Secretariat. In particular, the Secretariat seeks guidance from Members that use toothfish tagging data on any additional descriptions and diagnostics that could be provided to facilitate the adoption of this change in tag-linking approach.

Exploratory fishing for toothfish (Dissostichus mawsoni) in East Antarctica (Divisions 58.4.1 and 58.4.2) began in 2003. Robust stock assessments and catch limits according to CCAMLR decision rules remain to be determined for these Divisions. WG-FSA-16/29 outlined the first multi-member toothfish exploratory fishery research plan up to 2017/18 for East Antarctica, which the Scientific Committee agreed was appropriate to achieve the research objectives (SC-CAMLR 2016, para. 3.244). Subsequent research progress including the evaluation of standard approaches to identify precautionary catch limits (WG-FSA-17 para. 4.28-4.38) and bycatch mitigation (Maschette et al. 2017), suggests a low risk profile for this fishery. Furthermore, examination of bycatch data and underwater video footage have not led to the identification of vulnerable marine ecosystem (VME) indicator species (Maschette et al. 2017, Eléaume et al. 2018). Here, we update the research plan for 2018/19 to 2021/22 (WG-FSA-18/59), in accordance with ANNEX 24-01/A, Format 2. This plan has been designed as a 4-year plan, based on the low risk profile of this fishery and to allow more time for review by Working Groups of major reporting and review years in non-stock-assessment years.

Compared to last year (WG-FSA-18/59), this research plan has been updated with 2019/20 operating details, the inclusion of modelling work under Objective 2, and a re-ordering of milestones under Objective 4.

Natural mortality (M) is a key parameter in fisheries stock assessments, relating directly to the productivity of a stock, stock status, and estimated precautionary yields. In the Ross Sea region stock assessment for Antarctic toothfish (Dissostichus mawsoni), M is assumed to be 0.13 y^-1 and constant across age and sex.

In 2018, the independent review of the Ross Sea region D. mawsoni stock assessment recommended that CCAMLR consider the robustness and reliability of estimating natural mortality in the stock assessment model. We undertake a preliminary investigation of estimating natural mortality using the assessment model from the Ross Sea region from 2017.

We estimated natural mortality as a single value for males and females combined, with a uniform prior within the base model used in 2017 for Antarctic toothfish in the Ross Sea region. The model MCMCs estimated M=0.11 y^-1 (0.09–0.13 y^-1) with B0 estimated to be 92 140 t (70 330–121 950 t); a higher B0 72 620 t (65 040–81 050 t) when compared to the 2017 base case where M=0.13 y^-1. The precision of the estimate of B₀ when estimating natural mortality was lower and estimated the precautionary yield higher (3419 t compared with 3258 t). MPD simulations suggested that when the rate of natural mortality was assumed in an operating model, it was estimated with relatively high precision and with no bias.

Further investigations will need to be carried out to consider the effect on model fits and residuals and if robust estimates of the rate of natural mortality can be achieved using MCMC simulations. We recommend that analyses exploring the effect of the model-based estimate of M, including values of natural mortality that vary by age and sex, should be considered in future stock assessment sensitivity analyses

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. The annual survey has been conducted since 2012, with a revised proposal presented in 2017 for five years (2018–2022). The objectives of the survey included monitoring the abundance and age structure of sub-adult (≤ 110 cm TL) toothfish in the south of SSRUs 881.J and 881.L in the southern Ross Sea (Strata A–C) using standardised gear in a standardised manner; and monitoring trends in larger (large sub-adult and adult) toothfish in two areas (both situated in SSRU 881.M) of importance to mammalian toothfish predators: McMurdo Sound in 2018, and Terra Nova Bay surveyed in 2019. The estimated relative biomass index of toothfish showed an increase to the highest in the survey time series. Among the other survey objectives, the survey also released Popoff Satellite Archival Transmitters (PSATs) on toothfish throughout the survey area and tested a remote underwater camera to document benthic habitats where fishing occurs. Notification of research for the 2020 fixed-effort survey is included with the agreed catch limit of 45 t.