Reducing fish and invertebrate by-catch in targeted fisheries is an element of a precautionary approach to the management of Antarctic living resources. At the same time establishing by-catch limits sometimes could block in fact the research activities in certain marine areas. It is a reason to consider establishing by-catch limits for each separate research survey taking into account a research approach, abandoning the universal approach like reflected in the Conservation Measure 33-03.
Abstract:
The Scientific Committee considered the assessment of Dissostichus spp. in data-poor fisheries to be of a high priority (SC-CAMLR-XXIX, paragraphs 3.125 to 3.145). The use of different gear types for the implementation of a multi-Member research on Dissostichus spp. in East Antarctica (Divisions 58.4.1 and 58.4.2) in the seasons 2011/12 - 2017/18 is a critical factor for their efficiency and reliability. In the context of the discussion of the Scientific Committee (SC-CAMLR-XXXVII p.3.338-3.144; SC-CAMLR-XXXVIII p. 318, 3.119; SC-CAMLR-XXXIX p.4.10) we propose the research program on Dissostichus spp by the multi-vessels in Divisions 58.4.1 for seasons 2021/22-2023/24 based on standardized sampling longline gear and survey stratified design.
Abstract:
Fishing for Patagonian toothfish (Dissostichus eleginoides) has been carried out in Subarea 48.3 continually for more than 40 years, including more than 25 years under CCAMLR
management.
This paper reviews the long-term decline in the size structure of Patagonian toothfish (Dissostichus eleginoides) observed in longline catches taken in Subarea 48.3. It was noted that from the start of the 2000s until now, longline fishing in Subarea 48.3 has targeted immature fish smaller than 100 cm. The issue of non-rational use of the Patagonian toothfish stock in Subarea 48.3 is examined
Abstract:
The SC-CAMLR last estimated a precautionary harvest rate (gamma) used for management advice in the Area 48 krill fisheries in 2007 (SC-CAMLR, 2007 Annex 4 paras. 2.38-2.39). Subsequently, a range of various methods have been tried, with limited success, to produce both input parameters and stock assessments which can be used for management advice. Following the work plan outlined by SC-CAMLR (2019, Annex 4 paras. 2.60 – 2.64) endorsed by the Commission (CCAMLR, 2019, para. 5.53) the Generalised Yield Model (GYM) software was reimplemented in R as the Grym package, with the intention of updating the previous krill assessment. However, the methods used to estimate some input parameters to the previous assessment were not documented in detail, and there remains considerable ambiguity as to how to compute these inputs, and how these inputs are used within the assessment simulations.
Here we aim to clarify what each parameter within the Grym models are used for, and where possible provide examples as to how they have been calculated.
Abstract:
WG-SAM-2021 and WG-EMM-2021 reviewed available information for krill assessment simulations in Subarea 48.1 using the Grym. Whilst no agreement on parameters was achieved at WG-SAM-2021, the Working Group agreed that an ensemble approach using multiple parameter value combinations could be used (WG-SAM-2021, paras 3.21-3.22.)
WG-EMM-2021 provided initial parameters for the assessment simulations noting that alternate parameters could be tested to compare (WG-EMM-2021, paras 2.32-2.33 and Table 1).
Here we present the results of model ensembles for values either provided directly to the CCAMLR e-group on ‘GYM/Grym assessment model development’, or calculated based upon data submitted to the e-group. Code and outputs of the models are available on github (https://github.com/ccamlr/Grym_Base_Case /tree/Simulations).
Abstract:
A collaborative research program has been undertaken by Japan and South Africa since 2013 to enhance data collection and analysis in the subarea 48.6 under CM 21-02. Spain joined the proposal starting from 2018/19 fishing season in order to contribute to the data acquisition and to speed up the integrated assessments of the Antarctic toothfish (Dissostichus mawsoni) stock in this subarea (WG-FSA-18/34).
The continuation of the three-member research proposal for 2021/22 season is presented to ensure continuity of previous research activities. Data and investigations about the population structure and various demographic parameters of D. mawsoni using trotline (JPN and ZAF) and Spanish longline (ESP) gears, established tagging techniques, pop-up tags and genetic analysis will provide the basis for the development of spatial population models and assessments in support of management advice. An Integrated Stock Assessment (ISA) which takes into account the tag time series from southern research areas of Subarea 48.6 is going to be continually developed until the end of the 2023/24 season.
Based on suggestion from WG-SAM-2021 (report of WG-SAM-2021, para 8.4), the research plan have been revised as follows:
Explaining the importance of understanding stock connectivity between research blocks in the area (seamounts versus continental shelf),
indicating further details about how the stock structure will be represented in the planned CASAL assessment for the region,
increasing the otolith sampling rate from “10 otoliths per 5 cm length bin” to “20 otolith per 5 cm length bin), and
indicating minimum sampling requirements for by-catch species and designed to meet the research objectives.
The WG-SAM-2021 recalled that a structured fishing design was necessary to optimise tagging performance evaluation (report of WG-SAM-2021, para 8.4). However, as already described in 3(a) “Research survey/fishing design”, the area is not suitable to set a stratified sampling design as the fishing grounds with broad environmental characteristics such as a complex of seamounts, hills and ridges is expected to be small relative to the size of the research block. Therefore, no depth stratification is proposed in the current research plan.
The updated CCAMLR Research Plan – Research Proponent Self-Assessment can be found in Appendix 1.
There is no abstract available for this document.
Abstract:
Here, we provide diagnostic plots for the 2021 assessment model for Kerguelen Island EEZ Patagonian toothfish (Dissostichus eleginoides) presented in Massiot-Granier et al. (2021a), following the recommendations of WG-SAM-2015 (SC-CAMLR-XXXIV 2015 Annex 5). The stock assessment model is described in Massiot-Granier et al. (2021a), and a detailed description of the stock area, stock assessment methods and the stock assessment parameters are given in MassiotGranier et al. (2021b).
Abstract:
This paper presents an updated stock assessment for the Patagonian toothfish (Dissostichus eleginoides) fishery of the Kerguelen Islands EEZ, CCAMLR Division 58.5.1. It includes commercial fishery data up to the end of the season 2019/2020 (end of August 2020). The updated assessment model is based on the best available data and includes abundance estimates from random stratified trawl surveys (POKER, 2006, 2010, 2013 and 2017), longline tag-release and tag-recapture data from 2007 to 2020 and priors and estimates on model
parameters such as life traits (e.g. growth, maturity and natural mortality). It also uses commercial data that account for fish removals (fishing mortality and depredation) and support the estimation of year class strength (YCS) and selectivity functions.
Compared to the previous assessment that was presented to WG-FSA 19 (MassiotGranier et al., 2019), this assessment accounts for (1) updated catch and biological data (2019/2020), (2) updated age data from a new 4-year reading program, (3) updated priors on YCS and period of estimation (4) and updated depredation rate. All model runs were conducted using CASAL 2.30 2012-03-21 rev. 4648, that was agreed on by WG-SAM-14.
The updated model leads to a higher estimate of the virgin spawning stock biomass SSB0 than in 2019 with an estimate of 233 130 tons (95% CI: 207 030 – 265 460). The estimate of the current SSB status of the stock is 68,8% (95% CI: 64,5% - 73,1%) and the current catch limit meets the CCAMLR decision rules.
Abstract:
This paper presents an updated stock assessment for the Patagonian toothfish (Dissostichus eleginoides) fishery of the Crozet Islands, CCAMLR sub-area 58.6, with data up to the end of the season 2019/2020 (End of August 2020). This updated assessment model is based on the best available data and includes longline tag-release and tag-recapture data from 2007 to 2020 and priors and estimates on life traits model parameters (e.g. growth, maturity and natural mortality). It also uses commercial data that account for fish removals (fishing mortality and depredation) and support the estimation of their associated selectivity functions.
Compared to the previous assessment presented at WG-FSA 19 (Massiot-Granier et al., 2019, WG-FSA-2019/57 Rev. 1), this assessment accounts for (1) updated data (2019/2020) and (2) updated depredation rates. All model runs were conducted with the CASAL 2.30 2012-
03-21 rev. 4648, that was agreed on by WG-SAM-14.
The updated model leads to equivalent estimate of the virgin spawning stock biomass SSB0 than the one obtained in 2019, with an estimate of 55 740 tons (49 220 - 60 500 tons). The estimate of the current SSB status of the stock is 65,2% (61.4 % - 68.5 %) and the current catch limit satisfies the CCAMLR decision rules.