CCAMLR

Russian Federation is going to continue investigation for toothfish in Ross Sea. The previous Russian program was undertaken in the Subarea 88.2 in 2010-2012. This paper presents the   research program in the frame of the research and monitoring associated with the RSRMPA.

Russian research program have objectives to investigate the life-cycle, distribution and movement, biological parameters and stock structure of Dissostichus species in the eastern part of the Ross Sea over shelf and continental slope within the Subarea 88.2 A.  The tagging toothfish and recapture tagged fishes   to be in focus.  The study area covered by proposed investigations is located in the Special Research Zone of the RSRMPA. Proposals include the priority elements for scientific research and monitoring associated with the Ross Sea region marine protected area. 

The research program shall be conducted in the Special Research Zone during 2017-2027 or the first reference period for existence of the RSRMPA.   This program provides possibility   for collaborative investigations in the Special Research Zone by Russian vessel and vessels from other CCAMLR country-members. Implementation of this program can be started in the forthcoming season 2017/18.    

Exploratory fishing in Division 58.4.3.a is conducted by two vessels using longlines: “Shinsei Maru No. 3” (Japan) and the “Saint André” (France), since 2012. Precautionary management arrangements are in place in Division 58.4.3.a (Conservation Measures 41-05 and 41-11), while data are collected to provide a robust stock assessment and catch limits. A research plan jointly written by France and Japan has been submitted to WG-SAM-17, which included research objectives, methods and milestones in accordance with Conservation Measure 41-06 and associated measures. The main objective of this paper is to provide an overview of the data collected in Division 58.4.3a up to the CCAMLR fishing season 2016/17.

The Republic of Chile completely revised its initial plan for a three-year project to study the distribution, abundance and biological characteristics of Antarctic demersal fish communities after the first survey had been undertaken in 2016. The revised proposal is planned to run from 2018 to 2020. Based on the experience gained in the first phase of research and recommendations made by WG-SAM-16 and WF-FSA-16, a revised proposal for a random, stratified trawl survey to be undertaken in Subareas 48.1 and 48.2 in accordance with CM-24-01 is provided. The objective of this research survey is to determine the distribution, abundance, and size composition of demersal finfish in Subareas 48.1 and 48.2. In this revised proposal, the study area includes the continental shelf of Elephant Island and of South Orkney Islands, between 100 and 500 m depth (Depth strata: 101-200 m, 201-260 m; 261-320 m, 320-380 m, 381-440, and 441-500 m). Sampling will be conducted using bottom trawl nets, with stations in the same approximate geographic coordinates as those used by the R/V Polarstern around Elephant Island (Kock & Jones, 2012) and the R/V Yuzhmorgeologiya around the South Orkney Islands (Jones & Kock, 2009). This will provide valuable information that will allow a comparison with the data collected by these two previous surveys. With the data obtained in each Subarea, size composition, density and standing stock biomass of fish resources will be determined using the delta-lognormal maximum likelihood estimator. Also, demersal habitats and biological data will be collected routinely on each station: total length and weight, sex and maturity stage and biological samples (stomachs, gonads and otoliths), for the main species of demersal finfish captured during the survey.

Ukraine proposes to carry out a scientific survey of Dissostichus spp. by bottom longline in the eastern part of Subarea 48.1 with a partial (insignificant area) covering the area under investigation in Subareas 48.2 and 48.5.

Submitted format for reporting finfish research proposals of the Ukraine in Subarea 48.1 in 2018.  

Submitted format for reporting finfish research proposals of the Ukraine in Subarea 88.3 in 2018.  

Japan and France made the next season’s (2017/18) research plan in research blocks 58.4.4b_1 and 58.4.4b_2 using the latest CCAMLR C2 and Observer data.

The estimated median stock size in block 58.4.4b_1 and 58.4.4b_2 was 855.39 and 1120.40, tonnes respectively, in Chapman method considering tags released in the last three years as effective for the biomass estimation. The estimated median stock size in block 58.4.4b_1 and 58.4.4b_2 was 485.65 and 500.05 tonnes, respectively, in CPUE analogy method (reference area: HIMI) using the relevant information of reference area (recent median CPUE, estimated biomass and updated area size) recommended in the WG-SAM-16/18 Rev.1.

We propose to continue the current research operation for the next fishing season with the same survey design and total sample size of 70 tonnes to further strengthen the stock assessments in the area. On the other hand, Japan will examine the change of survey design from 2017/18 season considering change of CCAMLR's regulatory framework.

Following WG-SAM-16/42 Rev. 1, we updated the analysis on the sea-ice concentration of the period (2002-2017 until April) for 48.6_4 and 48.6_5. In addition, we also analyze the ice concentration of 58.4.2 to examine accessibility there for fishing vessels as candidate for a new research block. This research block is hypothesized as one of spawning grounds for TOA by Taki (WG-FSA-16/32 Rev. 1) and hence it should be covered by research for stock assessment in the near future.

Research block 48.6_2 is set in a limited part of the large-scale ridge which runs from northeast to southwest. The fishing vessels usually cannot complete sampling catch limit (CL) and accordingly they leave substantial amount of CL unfished in the research block because of limited spatial range and the low CPUE there. To enhance utilization of CL for stock assessment there, we would like to propose the extension of 48.6_2 in the near future(WG-SAM-16/08).

Migration has the potential to violate the assumptions of tag recapture models used in the assessment of toothfish stocks. Evaluating the potential bias introduced into stock assessments and tag-based biomass estimates when the distributions of tagged fish, fishing effort and the underlying stock distribution are spatially heterogeneous is currently one of the highest priorities of the Scientific Committee.

This study used a fisheries simulation model to evaluate the impacts of migration on a biomass estimates and sustainable catch limits from a closed population tag-based CASAL stock assessment. Our simulations demonstrated that emigration of tagged fish out of the assessed area results in initial and current spawning biomass, and stock status being over-estimated.

We then estimated migration of rates of Kerguelen Plateau Patagonian toothfish between the Divisions 58.5.1 and 58.5.2 using a catch-conditioned modification of the method used by Hilborn (1990). We considered longline tag releases from two periods, 2007-2014 and 2009-2014 and used tag recaptures to 2015 in both cases. The annual migration rate from Division 58.5.2 to 58.5.1 was estimated to be 1.1% using longline releases from 2007-2014 and 0.7% using longline releases from 2009-2014. The annual migration rate from Division 58.5.1 to 58.5.2 was estimated to be 0.4% and was insensitive to the time period of longline tag releases used.

For annual migration rates <2%, consistent with those we observed in Patagonian toothfish on the Kerguelen Plateau, bias in spawning biomass estimates from simulations was <5%. We demonstrated that the bias can be corrected by increasing the tag-shedding parameter in the stock assessment by the value of the migration rate, providing a simple yet effective approach to correct for the effects of emigration. The key benefit of making such an ad-hoc increase to the tag-shedding parameter is that it avoids the need to develop new assessment frameworks to account for emigration.

The impact of increasing the tag-shedding parameter in the 2015 assessment of Division 58.5.2 toothfish by 1% would have reduced the unfished spawning stock biomass by around 1.4% and the TAC by 3.8%.

We recommend that for tag-based assessments, the tag-shedding parameter should be increased by the estimated migration rate to adjust for migration related bias.