CCAMLR

This paper frames a discussion for improving the assessment of toothfish abundance for SSRUs 88.2C–G. We initially provide a characterisation of the fishery and a summary of available tagging and length frequency data. Although more than 700 tagged fish have been released in this region, only 2 fish have been recaptured. It is likely that the lack of tag recaptures in this region has been caused primarily by the poor spatial overlap of released tagged fish with subsequent fishing effort.

By drawing on the success of tagging programmes in other CCAMLR fisheries, we develop an approach for improving the spatial overlap of the location of tagged fish and subsequent fishing effort. We identify four main grounds previously fished in SSRUs 88.2C–G. An upper catch limit could be set for each of these grounds based on historic CPUE and a maximum local exploitation rate. It should be noted that the catch limit for SSRUs 88.2C–G will be constrained by the total catch limit for the wider Amundsen Sea stock (SSRUs 88.2C–H) and a subjective decision regarding how it will be split between the 88.2H and 88.2C–G fisheries. We then explore mechanisms for encouraging vessels to complete some or all of their sets within these previously fished grounds. Noting the relatively small number of tags currently available for recapture in this region we further recommend that the tagging rate in this area be increased to 3 tags per tonne in the short term to obtain more precise estimates of abundance and improved data indicative of stock structure.

Catch, effort, and mark-recapture data for Antarctic toothfish from individual seamount features in SSRU 88.2H were analysed to compare multiple raw indicators of biomass trends in isolated local areas. These metrics were also calculated for SSRU 88.2H as a whole. The analyses indicate that:

• Fish seldom move among seamounts within the complex, and residence time on particular seamounts is typically 1-2 years before fish depart from these seamounts, presumably back to the slope SSRUs. Therefore, it is recommended that the stock assessment include only recaptures of tagged fish that have been at liberty for less than 2 years, and that data from the Amundsen Sea slope SSRUs (88.2C–G) are included in the stock assessment along with 88.2H.
• Fishing has occurred on almost every seamount in every year, and no evidence for serial depletion or spatial patterns that would produce a current bias in recapture probability among seamounts was found.
• Single-season tag recapture rates exceeding 20% on some seamounts suggest relatively high local exploitation rates and the potential for localized depletion on some seamounts.
• Results from opportunistic post-hoc Leslie depletion analyses conflicted with other biomass indicators and suggested that opportunistic CPUE-derived abundance measures derived from Olympic fishery catch data are unlikely to index abundance at small temporal and spatial scales.
• Although indicative biomass as estimated by the CPUE by seabed analogy method produces values that vary markedly depending on the choice of reference area, the method produced lower biomass estimates than mark-recapture estimates when based on adequate sample sizes for this seamount fishery.

We review the stock structure of Antarctic toothfish in Statistical Area 88 with the aim of characterising the likely stock boundaries relative to stock assessments. We include information from genetic studies, otolith microchemistry, stable isotopes, tagging, size and age structure, growth dynamics, and egg and larval dispersal simulations. Taken together, the information suggests two biological stocks with limited mixing, especially at adult stages: a Ross Sea Region stock and an Amundsen Sea Region stock. The Amundsen Sea stock likely includes juveniles and adults along the continental margin in the Bellingshausen Sea (SSRUs 88.3A–D), SSRUs 88.2C–G, and a spawning region in the seamount complex of SSRU 88.2H. Key information needs to further understand stock structure include characterising the movement patterns and linkages of Antarctic toothfish in the 80–120 cm size range, throughout the continental margin SSRUs of the Amundsen Sea (i.e. SSRUs 88.2C–G). We recommend that the Ross Sea Region stock assessment boundaries remain as Subarea 88.1 plus SSRUs 88.2A–B and that the Amundsen Sea Region boundaries include SSRUs 88.2C–H.  Further research to better elucidate the proper stock affiliation of adjacent portions of the Bellingshausen Sea (SSRUs 88.3A-D) and juveniles in SSRUs 88.2C–G is a priority.

A research proposal to continue the southern Ross Sea subadult toothfish survey is presented. The survey will focus on estimating relative abundance in the core strata (A, B, C) in SSRUs 88.1 J and 88.1L. It will also carry out 15 exploratory sets in a newly defined stratum K in Terra Nova Bay. Survey timing and methods will remain the same as in previous years, and the number of sets will be retained at a total of 60 sets. A nominal catch limit of 68 tonnes, to be taken from the shelf catch limit for the 2014/15 fishing year is requested for the survey.

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. The first survey was completed in February 2012 (), and the second survey was completed in February 2013 (Parker et al. 2013). In this paper we provide preliminary results of the third survey in the time series.

The objectives of this third survey were:
(i)    To carry out a longline survey to monitor subadult toothfish in the southern Ross Sea (strata A–C) using standardised gear in a standardised manner; and
(ii)    To sample additional experimental stations in an adjacent area to identify areas of high subadult abundance which could be included as strata in future annual surveys.

The survey was successful in completing all the planned stations. The catch composition was similar to the previous surveys, although raw catch rates were down in strata B and C. Standardised catch rates for the core strata were similar to 2013 and down on 2012, although not significantly. Experimental stratum I showed larger fish than in the other strata, in particular close to Ross Island in the south and in the north-eastern side of that stratum.

Further results will be provided at WG-FSA-14, including age data and comparison with commercial catches in 2014.

Proposed Research plan for the survey of Ukrainian longliner in 48.2 subarea.

Most things related to Dissostichus spp. in the eastern side of Antarctic has not been known well as namely the area is data poor areas. In the Division 58.4.1 there are two stocks; one extends from the SSRU 58.4.1C to the SSRU 58.4.2A, and the other one to the SSRU 58.4.1H. The population sizes were vulnerable with a big range of about 1,000-2,000 t per SSRU in 58.4.1 and 100-1,500 t per SSRU in 58.4.2. During the 2004-2014 fishing seasons in Division 58.4.1, 58.4.2 and Subarea 48.6, 17,390 Dissostichus spp. were tagged and released, but only 113 fishes among them have been recaptured which were not enough data to estimate stock biomass for considering the precautionary catch limit. Therefore, the catch limits that the meeting got in 2013 meetings increased to get more recapture. The food-web of Dissostichus spp. has started to be studied in the southern Ross Sea. Some studies on biology of the fish have been evaluated, but those are not enough to assess the stocks and consider proper management measures. Based on CCAMLR’s fishery report, the eastern area is still data-poor area showing low recapture rate. Consequently, providing catch and effort data from the area, analysing biological samples, and collecting recapture data focusing on SSRUs in Division 58.4.1, 58.4.2 and Subarea 48.6 is very important.

The Korean scientists collected and analysed the catch, effort, and biological data such as length, weight, gonadal development, and muscle by NO. 3 INSUNG in Division 58.4.1 during 2012/2013 season. However, the results were still not good enough according to lack of data because of the bad sea-ice condition for the survey. Therefore, we will extend the research area and sample size of catch and fishing efforts, and biological data to get more accuracy and effective results to manage the eastern side area of Antarctic.

Therefore, Korea notifies the participation in exploratory fishery for Dissostichus spp. in the SSRUs in Division 58.4.1, 58.4.2 and Subarea 48.6 from 2014/2015 season to 2018/2019 using Korean commercial bottom longline vessel, KINGSTAR belonged to Sunwoo Company in accordance with paragraph of CM 24-01 and paragraph 6 (iii) of CM 21-02 to collect the catch and effort, CTD, tagged and released, recaptured data including archival tag, biological data for estimating biomass for Dissostichus spp. using CASAL and evaluating migration and distribution pattern by developmental maturity and size stages.

The integrated modeling framework for Antarctic krill (Euphausia superba)  has been extended to include estimates of krill growth consistent with survey data and to use multi-nation survey data collected from 1981 to 2014 near the Antarctic Peninsula. Four models of the population dynamics of Antarctic krill in Subarea 48.1 based on different aggregations of the data are described to illustrate the capabilities of the framework. Survey data collected by Germany (RMT8 net sampling from 1981 to 1989), the US AMLR program (IKMT net samples from 1992 to 2013 and 3-channel hydroacoustic transects from 1996 to 2011) and Peru (IKMT sampling in 2014) are organized into different temporal aggregations (annual, seasonal, monthly) and supplied to the framework to estimate population parameters.  One data set contained only the IKMT summer data. Three other datasets each contained all the RMT8, IKMT, and hydroacoustic data arranged in different temporal groupings (annual, summer-winter, monthly). The effects of the different ways of aggregating the data on the model estimates are evaluated both for the original data and using simulated data. Models based only on IKMT summer data or on all data sources aggregated annually produced similar estimates of population parameters. All models fit the simulated data closely. Three of the four models successfully reproduced the original estimates for spawning biomass and recruitment from the simulated data. The model using the most complex separation of the data into 7 different surveys failed to reproduce the correct estimates of recruitment and spawning biomass from the simulated data. Plans for extending the models and data in the upcoming year include modifying the code to make forward projections, incorporating data from the krill fisheries and observer program, and possibly begin to incorporate predator diet compositions.

The longline fishery for toothfish in the Ross Sea currently operates as an Olympic fishery. The number of vessels operating in the fishery has progressively increased in recent years yet overall catch limits have remained relatively stable and as a consequence the fishing opportunities for individual vessels have reduced. This report investigates recent trends in the development of the Ross Sea toothfish fishery with specific focus on capacity related issues using information derived from the CCAMLR C2 catch and effort data. Managers need to assess and monitor capacity and capacity utilisation in a fishery in order to be aware of the pressures within the fishery as well as the trends and changes that are impacted by management measures. There is therefore a requirement for the routine production of standard metrics of capacity and capacity utilisation that can be used to monitor trends in the fishery. Such metrics could be routinely produced by the CCAMLR secretariat using the CCAMLR C2 data.

Regarding the low levels of stocks of Dissostichus spp. and the high levels of IUU fishing, CCAMLR decided to close the fishery in 2002 in division 58.4.4. Since 2008 only one vessel, Shinsei maru No. 3, has conducted research fishing in accordance with a research plan submitted under CM 24-01. France notifies its wish to collaborate in this research fishery over the coming years in order to participate in the tagging program and achieve a robust stock assessment. The aim is to provide advice on a catch limit according to CCAMLR decision rules and allow an earlier decision to reopen this area. This paper presents a proposal for a research plan for 2014/2015. For SSRU C, further developments of the assessment of Dissostichus eleginoides using a CASAL model and a simple Petersen biomass estimate derived from tagging data are proposed. The CASAL model structure is improved with three scenarios tested 1/ base case model without IUU catch; 2/ including 22% of IUU catch supposed in Division 58.4.4; 3/ IUU catch estimated within the model. For the run 3/, B0 is estimated at around 640 tonnes and the estimate of total amount of IUU catch is 160 tons. With Petersen’s method, geometric mean stock abundance estimate is 434 tons. Stock size of D. eleginoides in SSRU D was only estimated using comparative CPUE method with a value of 739 tons. Given no sufficient robust results and a lack of data recapture, the total research catch limits agreed in 2013 for SSRU C (25 tons) and for SSRU D (35 tons) were likely to result in sufficient tag recaptures to substantially refine the stock assessment.