CCAMLR

The Antarctic toothfish stock assessment for the Ross Sea region (Subareas 88.1 and 88.2AB) will be updated in 2017. The introduction of CM 91-05 (the Ross Sea region Marine Protected Area) will require modifications to the previous method the estimation of catch splits in the calculation of precautionary yields. In addition, work will need to be carried out in the longer term that consider how the assessment will need to be modified to respond to changes in the fishing catch and effort distributions that may result from the implementation of the Ross Sea region MPA.

An update of the 2015 stock assessment is proposed for the 2017 stock assessment which will maintain the current structure of the model while including updated catch, age-frequency, and tag-release and recapture data. Yield projections should be run that incorporate short term catch split options as required by CM 91-05. Additional options could also be developed for catch splits between the shelf, slope and north areas prior to the 2019 assessment. Sensitivities to a base case model that investigate the robustness of model assumptions or arise from the considerations of model diagnostics should also be conducted.

The Amundsen Sea region (ASR) is currently managed under a research plan, which has shown promising results to date, with 8 interseason tags recaptured in the South area in 2016 and 12 (preliminary recaptures) in 2017. The aim of this paper is to ascertain when the Amundsen Sea region stock assessment model is likely to provide management advice, and to investigate the effects of using either two independent single-area models or a two-area model.

We used simulations to investigate the expected precision in estimates of biomass, the likely biases, and to set expectations for mark-recapture data for the next few years to predict progress towards a robust assessment model using the two-area model. The models showed that using two independent models lead to higher estimates of biomass in the North and lower estimates of biomass in the South, but that the two independent models fitted the data poorly. Simulations suggest that the current research plan with the current levels of catch and tagging rate is likely to deliver the information that would generate a robust estimate of biomass in the ASR in the future. We also found that it is likely that we would observe very few tags moving between the areas and that increasing the tagging rate in the South would result in an increase in bias but no improvement in the precision of the estimation of stock biomass.

We therefore recommend (i) future work using independent methods to understand toothfish movement within the ASR (such as PSAT tags or otolith microchemistry), and (ii) the current research plan be continued for the next season, and (iii) a two-area model continue to be developed to assess the ASR for 2018, as recommended by Scientific Committee in 2016.

At its 2011 meeting, the Scientific Committee agreed that a time series of relative abundance from a well-designed survey could be a useful input into the Ross Sea stock assessment model. In this paper we provide results of the sixth annual survey in the time series. The objectives of this survey included monitoring 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 predators: Terra Nova Bay in 2017, with McMurdo Sound surveyed in 2016.

The estimated relative biomass index of toothfish for the core strata showed an increase to the maximum observed in the time series. Scaled length frequencies for the core strata indicate the progression of a strong year class that appears in 2012 progressing through each year, with the appearance of a second strong cohort in 2015. The decline in relative biomass during the survey time series is consistent with the decline in abundance of this 2012 cohort through time, through mortality and the movement of older fish out of the survey core area, as well as the weaker subsequent year classes. A second, strong cohort is evident entering the population in 2015, with a subsequent increase in biomass in 2016 and 2017. These results suggest the surveys are indexing local abundance and age structure, and are providing a reliable means of monitoring recruitment, estimating recruitment availability and year class strength.

Higher than expected catch rates early in the survey necessitated the reduction of station density in the core strata to avoid exceeding the catch limit. As a result of sampling fewer stations in the core strata, the variance of survey estimates was higher than in previous surveys. The higher than expected catches required an adaptive survey design to maintain a scientifically robust and comparable survey whilst constraining catch to below the catch limit. Principles to follow while adapting the survey to unexpected circumstances may be useful for others conducting longline surveys in CCAMLR fisheries.

This paper proposes to continue the Ross Sea shelf toothfish survey for the next five years, 2018–2022. The first objective of the survey is to monitor toothfish recruitment in the southern Ross Sea (core strata). This is a continuation of the yearly time series of research surveys of these strata carried out since 2012. It is important to continue the time series as the data collected provide essential input to the stock assessment to estimate year class strength which is used to inform management decisions. The second objective is to monitor trends in larger (large sub-adult and adult) toothfish abundance in alternate years in McMurdo Sound and Terra Nova Bay where toothfish may form an important part of the diet of Type C killer whales and Weddell seals. The third objective is to collect and analyse a wide range of data and samples from these areas (e.g. benthic invertebrates, stomach and tissue samples, and acoustic data). Both objectives two and three are specified as high priority research topics in the research and monitoring plan for the Ross Sea region MPA. The survey design will remain consistent with previous years. Different catch limits are requested on alternate year to account for the different catch rates in McMurdo Sound and Terra Nova Bay. The results of each survey and trends in the time series will be presented to WG-FSA for review each year and the results included in the stock assessment. A full review will be completed and presented to WG-SAM, WG-EMM, and WG-FSA in 2022.

New Zealand proposes to contribute to a multi-member research plan to sample the toothfish population in Subarea 88.3. Although this has been written as a stand-alone proposal, the intention is to develop a single co-ordinated research plan with Korea and any other members who may wish to conduct research in this subarea. There is considerable uncertainty about the abundance of Antarctic toothfish in Subarea 88.3 and the Scientific Committee has requested members complete research in this area to address that uncertainty. There is also considerable uncertainty about the stock structure of Antarctic toothfish in this subarea – and their relationship to the rest of the Pacific Sector. Korea have already developed a research plan for this subarea, but there are several regions and features which are not currently being surveyed. This research proposal is designed to complement Korea’s research plan by focusing research on the abundance of toothfish on two of the northern features, as well as parts of the slope and southern shelf where little fishing has occurred. The two main objectives of the proposal are: (i) to determine the abundance of Antarctic toothfish in Subarea 88.3; and (ii) to improve understanding of stock structure of toothfish in this area. To complete the effort-limited survey a total of 65 sets is required. We estimate a maximum catch of 95 tonnes may be required to ensure the survey objectives can be met.

In 2016, changes to the methods used by CCAMLR to estimate biomass in research blocks resulted in conflicting estimates of biomass between the CPUE by seabed area and the Chapman estimate. The Scientific Committee requested that the changes to the methods be reviewed, that scientific rational for the different biomass estimates be provided.

In this paper, we develop a modified CPUE by seabed area method that improves on the original CPUE by seabed area method for toothfish populations in research blocks. This uses local Chapman biomass estimates in the reference area instead of the stock biomass estimated by the stock assessment model as the reference biomass. We demonstrate evidence of a linear relationship between CPUE and fish density in the Ross Sea reference area for the first time. The resulting density estimates from Shelf/Slope and North habitat types from the Ross Sea can be used to estimate a CPUE by seabed area biomass in designated research blocks.

We also develop a Bayesian approach that combines the information from the CPUE by seabed area biomass analogy and Chapman biomass estimates together in an integrated statistical to provide robust estimates of biomass in research blocks.

The CAMLR Scientific Committee in 2016 reviewed three scientific background documents in support of the development of a CCAMLR MPA in the Weddell Sea. Germany was asked to carry out further work, in particular regarding the issues and questions raised at WG-EMM-16 and SC-CAMLR-XXXV. Here, the authors intend to update the CCAMLR Working Groups on the current state of the work carried out during the 2016/2017 intersessional period. Chapter 1 of this working group paper informs on the new data retrieval process. Chapter 2 presents the updated analyses of relevant data layers, including an update on the Antarctic toothfish habitat model. Chapter 3 provides a sensitivity analysis of the level of protection for Antarctic toothfish and other demersal fish that explores a range of protection-level scenarios. In this context, we show how the cost layer works. Subsequently, a revised Marxan approach based on the updated data layer is shown. In Chapter 4 we outline the way we transferred the results of the scientific analyses into the WSMPA borders and management zones.

At last year’s meeting, it was agreed that a five-year work plan for the Scientific Committee should be developed for consideration by the Scientific Committee in 2017 (SC-CAMLR-XXXV, paragraphs 13.8 to 13.20). It was agreed that the work should be led by the Chair of the Scientific Committee with input from the conveners of its working groups and that it should be made available for consideration by each working group prior to submission to the Scientific Committee.

This document represents the first stage in the development of the five-year work plan and draws on recommendations arising from SC-CAMLR-XXV and the 2016 Scientific Committee symposium (SC-CAMLR-XXXV/12). In particular, the plan has used the template of the five-year work plan of the ATCM CEP and considers a range of work ‘themes’ which arose from the SC symposium as priorities for the Scientific Committee. These broad themes are as follows:

• Target Stock- Assessments to estimate sustainable yield in established/assessed fisheries
• Target Stock-Development of management advice consistent with Article II for data-limited fisheries
• Ecosystem based management of Southern Ocean krill resources
• Minimisation of risks of change to the ecosystem by CCAMLR fisheries – Vertebrate by-catch and VME in CCAMLR fisheries
• Spatial management of impacts on the Antarctic ecosystem
• Data acquisition and management.

Within each theme, a range of tasks have been identified along with science topics to be considered in order to carry out the tasks. A timetable of work within each theme has then shown under which working group the tasks will fall. These tasks are based largely on table 1 of SC-CAMLR-XXXV along with consideration of discussion arising from SC-CAMLR-XXXIV/14.

It is intended that the final document will become a ‘living document’ that can be revised annually as the priorities of the SC develop and unforeseen issues that require action from the SC may arise. It is intended that the document will also be publically available in order to promote a greater public understanding of the priorities and work of the Scientific Committee.

Ukraine proposes a plan for scientific research in Statistical Subarea 88.1 for vessels SIMEIZ, KOREIZ, CALIPSO, MARIGOLDS based on the provisions of paragraph 2 of Conservation Measure 91-05. Studies are expected to be conducted in the Special Research Zone (SRZ)

Korean research fishing was conducted in Subarea 88.3 from 11 January 2017 to 7 March 2017 in 2016/17 fishing season. The total number of fishing days are 38 of 56 days stayed in the fishing grounds. The total catch of D. mawsoni was 118,220 kg with 4,132 individuals, and their CPUE recorded 0.21 kg/hook. 957 individuals of D. mawsoni were tagged and released. Tagging rate and tag overlap statistics in Subarea 88.3 were 5.04 and 88%, respectively. Length frequency of D. mawsoni had a single mode of 150 cm range. The maturity of D. mawsoni dominated in stage 2 with 84.6 % of female and 73.1% of male during the survey period. To get biological information of species in detail, otolith, stomach contents, gonad and muscle were collected from each individual of D. mawsoni. We also collected temperature and salinity using CTD at 12 stations.