Full details of the latest stock assessment of southern bluefin tuna are available from the report of the most recent meeting of the CCSBT Scientific Committee:
A brief report on the Report on Biology, Stock Status and Management of Southern Bluefin Tuna is also available at:
Summary of the Latest Assessment
A summary of the stock assessment and stock status results from the 2011 meeting of the CCSBT’s Extended Scientific Committee (ESC) is as follows:-
- The current spawning stock biomass (SSB) remains very low (0.03-0.07 SSB0). However, the outlook for the stock is positive.
- There have been several positive recent signals about the outlook for the spawning stock. These include:
Stock
- Reduction in the total reported global catch;
- Current fishing mortality reduced and now below FMSY; and
- Confirmation of increases in longline CPUE since 2007.
Recruitment
- Increased scientific aerial survey and SAPUE indices (reflective of potentially improved recruitment of recent year classes); and
- Increased abundance of 1 year old SBT observed in the scientific aerial survey for the past three years and the troll survey in the most recent year.
- Recent recruitments (2005-2011) are estimated to be higher than previously and above the estimated stock-recruit curve, in contrast to the weak cohorts of 1999-2002. These estimates are driven by both the recent increases in CPUE and the scientific aerial survey data. Nevertheless, it will be some time before the recent stronger recruitments enter the spawning stock. Model results indicate that the spawning stock biomass is likely to increase after 2012.
- Increases in a number of CPUE indices in the most recent years, such as the New Zealand domestic fishery and Japanese longline fishery for age classes 4 and 5 suggest stronger year classes in recent years. Caution should nevertheless continue to be exercised in interpreting the longline CPUE data, where there is underlying uncertainty in the past data and regarding potential changes in fishing operation patterns since 2006, which remains to be resolved.
