Assessment of the Patagonian toothfish (D.eleginoides) in Subarea 48.3 indicates that the current status of the stock is at 52% of B0. Spawning biomass has been increasing in recent years. The 2008 year class is estimated to be well above average. Provisional projections indicate that a catch limit set at around 2,750 tonnes would be expected to keep the stock at or above 50% of B0 after 35 years with 50% probability, with less than 1% probability declining below 20% of B0 and would therefore be consistent with the CCAMLR decision rule.

The end of the 2014/15 season will see the completion of the third year of the multi-year research plan being jointly undertaken by Japan and South Africa in Subarea 48.6. The progress report presented at WG-SAM-15 (WG-SAM-15/50) has not been updated for WG-FSA as neither of the vessels undertaking the research returned to the study area over the winter.

WG-SAM-15 requested that a summary of the data collected over the past three years be prepared for WG-FSA-15. As the fishery related information such as distribution of effort, catch and tag releases and recaptures are already available in documents tabled at WG-SAM-15 (WG-SAM-15/06 and WG-SAM-15/50), this paper concentrates on summarising the biological data that has been collected. We also report on the otoliths from the Subarea that have been read.

The stocks of Antarctic toothfish, Dissostichus mawsoni were a relatively economically and ecologically important fishery resource in the waters of Antarctic. However, there is not enough data and information to assess the robust stocks and deliberate proper measurements for sustainable utilize, especially relate to diet and feeding strategy which may lead to think about ecosystem based stock assessments and fishery managements. Therefore, the Korean scientists analyze diet composition and feeding strategy of D. mawsoni in the research blocks 58.4.2-1, 58.4.1-2, 58.4.1-3, 58.4.1-4, and 58.4.1-5 as a part of Korean research plan for the exploratory longline fishery for Dissostichus spp. during 2014/2015 season. This study was carried out based on the results of stomach content identification of the D. mawsoni caught in the research blocks 58.4.2-1, 58.4.1-2, 58.4.1-3, 58.4.1-4, and 58.4.1-5 in CCAMLR Conversion Area from December 2014 to March 2015. The diet composition and feeding strategy of D.  mawsoni were studied using 549 specimens (74 to 181 cm in body length).  D. mawsoni is a carnivore and piscivorous fish that mainly consumed fishes, especially Macrourus spp. with 47.6% of the diet by weight.  Its diet also included small quantities of crustaceans, mollusks, and birds. In this study, fishes were the dominant prey item in all size classes (<100 cm (74-100 cm), n = 6; 100-120 cm, n = 31; 120-140 cm, n = 148; 140-160 cm, n = 221; 160 cm< (160-181 cm), n = 43). In the fish prey items, macrouidae were the dominant prey item in three size classes (120-140 cm, 140-160 cm, and 160 cm< (160-181 cm) The graphical method for feeding strategy revealed that D. mawsoni is an opportunistic and specialized predator on fishes and macrouidae, and showed narrow niche width.

The subarea 88.3 is a large area contained from 105°W to 70°W where has been closed to directed fishing following the results of a Chilean survey activities in 1998 (SC-CCAMLR-XVII/BG/7). Previous three research surveys conducted by the New Zealand and the Russian flagged vessels since 1998. It was noted that 8 D. Mawsoni were tagged by the New Zealand in the 2004/2005 season and 123 D. Mawsoni were tagged by Russian flagged vessels in the 2010/11 and 2011/12 season (WG-FSA-05/53, WG-FSA-11/36 & WG-FSA-12/13). It was also noted that no tagged fishes were recaptured during the previous research activities. Considering this large region, the Republic of Korea notes that only 95 research hauls and 131 tagged fishes from three research activities (in total since 1998) were not enough likely to recapture. it was further noted that there was no research activities more than two consecutive years in the past despite the Scientific Committee has agreed that research fishing should be conducted such that it results in an assessment of a stock in 3-4 years time (SC-CAMLR XXVIII, paragraphs 4.165).

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. During the 2004-2014 fishing seasons in Division 58.4.1, 4,998 Dissostichus spp. were tagged and released, but only 14 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 and 58.4.1C. 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 58.4.1is very important.

Korean research plans were endorsed by the Scientific Committee at SC-CAMLR-XXXIII. The Korean scientists collected and analysed the catch, effort, and biological data such as length, weight, gonadal development, and muscle by KINGSTAR in Divisions 58.4.1 and 58.4.2 in 2014/2015 season. Korea will also conduct the exploratory fishery with research plan for Dissostichus spp. in the SSRUs in Divisions 58.4.1 and 58.4.2 in 2015/2016 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.

In 2014, CCAMLR endorsed a TAC of 4410 t of Patagonian toothfish in Division 58.5.2. This report describes the recent fishing and data collection activities in the fishery. The fleet has expanded to include 6 vessels, 5 operating exclusively longline, and one dual purpose longliner/trawler. To enhance the tagging program that was established in 1998, the fleet has increased tagging rate in this Division from 2 tags/3 tonnes to 2 tags/tonne. Tag overlap statistics across the fleet have been consistently above 80% since 2012. Vessels have also explored new fishing grounds over recent seasons, considerably adding to information on the structure of the population. The ageing program at AAD has produced an additional 2559 estimates of age, for fish captured during the 2014 and 2015 Random Stratified Trawl survey, commercial fishing in 2013/14, and archived otoliths from tagged and recaptured fish from the 2009/10-2013/14 seasons. These samples have detected fish as old as 51 years, increasing the previous maximum age estimate of 42 years. These data have been used to develop age length keys and a revised growth function for inclusion in the 2015 revised stock assessment.

At WG-SAM-15, it was noted that 5 members, Australia, France, Japan, Korea and Spain had notified to conduct research in the exploratory toothfish fisheries off East Antarctica, covered by CCAMLR Divisions 58.4.1 and 58.4.2. This proposal seeks to establish an arrangement whereby all notified members have a catch allocation to undertake research, thereby avoiding Olympic fishing.

Incidence of odontocete depredation, involving sperm whales (Physeter microcephalus) and orcas (Orcinus orca) has been reported in nearly all of the Patagonian toothfish (Dissostichus eleginoides) longline fisheries in the Southern Ocean (Moir Clark and Agnew 2010, Tixier et al 2010, Soeffker and Tixier 2015, Söffker et al. 2015). The first reports of odontocete depredation in the Division 58.5.2 fishery date from 2011, and incidences have been reported in every season thereafter. The majority of  reports involve sperm whales, with a single sighting of orcas to date. There is a strong seasonal pattern to sperm whale presence, with depredation events confined to the months April-July, despite longlining activity occurring April-November. Currently, all vessels mitigate depredation by hauling lines once sperm whales are sighted, and steaming over 50 nautical miles before resetting gear. A collaborative project with depredation experts from France is currently being developed to monitor depredation behaviour across the Kerguelen Plateau and explore options for long term mitigation

This paper presents an updated assessment for the Patagonian toothfish (Dissostichus eleginoides) fishery at the Heard Island and the McDonald Islands in CCAMLR Division 58.5.2 with data until end of July 2015. The updated assessment model is based on the best available estimates of model parameters, the use of abundance estimates from a random stratified trawl survey (RSTS), longline tag-release data from 2012-2014 and longline tag-recapture data from 2013-2015, and auxiliary commercial composition data to aid with the estimation of year class strength and selectivity functions of the trawl, longline and trap sub-fisheries.

Compared to the 2014 assessment that was accepted by WG-FSA-14 to be used for management advice, this assessment takes into account the recommendations of WG-FSA-2014 and WG-SAM-2015, and incorporates (a) new fishery observations up to 2015 including new ageing data from the 2014-2015 RSTS and commercial fishery from 2009-2014, (b) tag-releases from 2014 and tag-recaptures from 2014 (complete) and 2015 (partial), (c) an updated growth model, (d) changes in priors for survey catchability q, unfished spawning biomass B₀ and year class strength, and (e) a split of the trawl sub-fishery into two periods. All model runs were conducted with the CASAL version 2.30-2012-03-21 that was agreed on by WG-SAM-14.

The updated assessment model leads to a smaller estimate of the virgin spawning stock biomass B₀ than that obtained in 2014, with an MCMC estimate of 87 077 tonnes (95% CI: 78 500-97 547 tonnes). Estimated SSB status in 2015 was 0.64 (95% CI: 0.59-0.69). Using this model, a catch limit of 3405 tonnes satisfies the CCAMLR decision rules. Similarly to the 2014 assessment, the projected stock remains above the target level for the entire projection period.

CASAL files are available here.