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Latest Stock Assessment
Details of the latest assessment of southern bluefin tuna (SBT), including updated fishery indicators, are available from the report of the Twenty Sixth meeting of the CCSBT Scientific Committee:
A brief report on the Report on Biology, Stock Status and Management of Southern Bluefin Tuna is available at:
The next full stock assessment for southern bluefin tuna is scheduled to be conducted during 2023.
Summary of the Latest Assessment
The Twenty Fifth Meeting of the Scientific Committee noted from the 2020 full stock assessment that:
- The stock, as indicated by relative Total Reproductive Output (TRO), is estimated to be 20% (16-24%; 80% P.I.);
- The stock remains below the level estimated to produce maximum sustainable yield (MSY);
- There has been improvement since previous stock assessments conducted in 2017 which indicated that relative TRO was at 13% (11-17% 80% PI);
- The fishing mortality rate is below the level associated with MSY; and
- The stock has been rebuilding by approximately 5% per year since the low point in 2009.
The 2020 assessment also indicated that the stock has increased from a low of 10% of initial TRO in 2009.
Summary of indicators
The review of indicators by the Extended Scientific Committee in 2021 is summarised below:
- Compared to the previous year, the indicators are mixed (some increased, some decreased, and others were neutral); however, there were no unusual signals nor suggestions of any reasons for concern. Overall, the longer term trends in the indicators are consistent with the most recent assessment that indicated a resource that is expected to continue increasing.
- Two age-1 abundance indices are derived from the trolling survey. The TRG recruitment index shows a somewhat decreasing trend from 2011 to 2021, and the TRP recruitment index recorded zero values in 2018 and 2019, suggesting some concern about potential low recruitment in recent years.
- The gene-tagging age 2 abundance estimate for 2019 increased compared to the estimates for 2017 and 2018.
- The Japanese longline nominal CPUE decreased in 2020 but was still above the 10-year mean. In contrast, the Japanese standardised CPUE series (for all vessels and for core vessels) increased.
- The standardised CPUE from the New Zealand domestic longline fishery increased.
- The Korean standardised CPUE in Areas 8 and 9 showed an increasing trend since the mid-2000s.
- For the standardised Taiwanese CPUE, the trends remained similar as in past but increased slightly in both areas (central-eastern and western) with updated data in 2020.
Annual Review of implementation of the CCSBT Management Procedure
The 2021 review of Exceptional Circumstances did not identify any new issues that affect implementation of the Management Procedure. The existing Exceptional Circumstance associated with the issue with the CPUE standardisation, identified in 2019, is being addressed through development of a new CPUE series, which will be available for the next TAC recommendation in 2022. There is no new information on unaccounted mortality. An update on the estimates of potential non-Member catches is planned for 2022. The Cape Town Procedure (CTP) has been designed to be robust to a level of non-reported catch that is higher than the current estimates (Report of SC 24, paragraph 92).
Given the review of Exceptional Circumstances, which did not identify any new issues, and planned actions under the meta-rules process to develop a new CPUE series to be used in the CTP, the Extended Scientific Committee recommends that the global TAC in 2022 should remain at 17,647 t.