Recommendations

For GYM assessments with proportional recruitment, we recommend to use:

• Formula-based methods for low variance in proportional recruitment;

• Simulation modelling for high variance in proportional recruitment to accurately reproduce mean and standard deviation;

as described in this paper and implemented in the Grym (open source package).

Abstract

Krill are a keystone species in the Southern Ocean food-web, and, as such, it is crucial to effectively manage the krill fishery to ensure its long-term sustainability. To assess the impacts of current harvesting pressures, evaluations rely on sampling and population modelling. Krill stock projections are developed with the Generalised Yield Model (GYM), which provides an assessment for stock status under current harvesting scenarios and various levels of uncertainties. One of the fundamental components of the GYM is the simulation of recruitment. De la Mare (1994) presents a proportional recruitment function for estimating krill recruitment based on estimates from field surveys. The De la Mare (1994) function uses estimates of the mean and variance of recruitment from survey data to determine the scaling of natural mortality and the distribution of random recruits that reproduce the observed mean and variance estimates. We evaluated De la Mare’s (1994) proportional recruitment function and found that for large variations in recruitment the function does not reproduce the observed mean proportion of recruits and its variance accurately. We review the deficiencies within the model and provide two alternative methods, which can support a wider range of values and possible extreme scenarios, such as years of low recruitment.

As part of the revision of the krill management approach, the Secretariat was tasked to estimate proportional recruitment indices in Subareas 48.1, 48.2 and 48.3 using the SISO (i.e., observer) krill length data collected onboard fishing vessels. This document summarizes the steps taken to estimate the mean and standard deviation of proportional recruitment in each Subarea, for potential use as inputs to the Grym (Maschette et al., 2020).

Preliminary biomass estimates for research blocks in data-limited fisheries and the resulting preliminary catch limits for the 2022 season have been determined using the trend analysis decision rules. The resulting preliminary catch limits are for illustrative purposes only and do not constitute recommendations.

Recommendations

(1) That this research plan with a revised sampling design within six existing research blocks in Division 58.4.1 and one existing research block in Division 58.4.2 be adopted.

(2) If directed fishing was not allowed in Division 58.4.1 in 2021/22, that this research plan for the exploratory fishery in Division 58.4.2 with one existing and one new research block be adopted.

Abstract

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 (SC-CAMLR-38/BG/10), this research plan has been updated with 2021/22 operating details, a change to the sampling design within existing research blocks, and a proposed new research block in Division 58.4.2 if directed fishing was not allowed in Division 58.4.1 in 2021/22. The updated ‘CCAMLR Research Plan – Research Proponent Self-Assessment’ can be found in Appendix 1, and the description of vessel tagging procedures following the survey questionnaire (see Comm Circ-21-54 and SC-Circ-21-68) in Appendix 3.

The Ross Sea shelf survey has been conducted annually since 2012, with the most recent revised proposal presented in 2017 and spanning five years (2018–2022). This paper:

• serves as notification for the 2022 survey under CM 24-01 following the survey design proposed in WG-SAM-17/39, and annual notifications in WG-FSA-18/41, WG-SAM-19/03, SC-CAMLR-39-BG-03.
• fulfils the requirement for a self-assessment of research proposals,
• provides updated information needed for CM 24-05,
• updates the milestone achievement table.

A research plan for Subarea 88.3 was commenced by Korea in 2016 under CM 24-01, New Zealand joined the proposal in 2017. The joint research proposal was for 3 years covering the period 2017/18, 2018/19 and 2019/20. It was designed to build on Korea’s previous research by continuing to focus on research blocks where tagged fish have previously been released on the slope, while also prospecting two of the northern seamount complexes and two boxes on the continental shelf, where no research has occurred. Following a proposal from the Ukraine to join the research plan in 2018, the Scientific Committee requested an integrated proposal be developed for all three Members (SC XXXVII paragraph 3.191). This proposal updates the final year (19/20 fishing season) of the research plan with the recommendation from the Scientific Committee to integrate the Ukrainian research with the Korean and New Zealand research plan. We propose to continue the research on Dissostichus spp. in Subarea 88.3 from 2021/22 to 2023/24. The main objective of the proposal is to determine the abundance and distribution of Antarctic toothfish in Subarea 88.3. Secondary objectives are to improve understanding of stock and population structures of toothfish in Statistical Area 88, to carry out calibration trials among the vessels, to collect data on the spatial and depth distributions of bycatch species, and to trial scientific electronic monitoring technologies.

Mackerel icefish (Champsocephalus gunnari) is one of the most common and widespread species of Antarctic fish. Ukraine proposes to conduct a survey of Champsocephalus gunnari in the statistical Subarea 48.2 by the midwater trawl. The main objective of the research is to determine the distribution and the abundance of Champsocephalus gunnari in the Subarea 48.2.

Authors present the acoustic data obtained on the R/V Atlantida cruise in 2020 to examine spatial and temporal variability of krill distribution. These data were collected in Subareas 48.1 and 48.2 using the repeated  transect system, including: local survey in Bransfield Strait and two mesoscale reference transects  (one is in the Elephant Island stratum and one is in the  Scotia Sea stratum  along longitude 50⁰ w ). Acoustic observations at the local survey and on each of the reference mesoscale transect were undertaken twice with an interval of about a month (34-36 days). Acoustic data collection and processing were completed in full compliance with CCAMLR recommendations (with references within WG-EMM-16/38; WG-EMM-11/20, ASAM-16/01) and accompanied by trawl sampling and environmental observations. There were no commercial vessels in the study area, excluding the effect of krill fishing on the observed distribution of krill. Significant temporal variability in the krill distribution were identified, both at the local survey area and at each repeated mesoscale transect. Such changes are demonstrated in estimates of the density, horizontal and vertical distribution of krill. The change in the krill biomass in the local area under consideration in Bransfield Strait was 792.6 thousand tons being accompanied by a change in the krill length composition. According to the authors, the observed temporal variability of krill distribution at different spatial scales is a consequence of the influence of the krill flux by the current.