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Title:

Next-generation Close-kin Mark Recapture: using SNPs to identify half-sibling pairs in Southern Bluefin Tuna and estimate abundance, mortality and selectivity

Project Number:

2016-044

Organisation:

CSIRO Oceans and Atmosphere Hobart

Principal Investigator:

Campbell Davies

Project Status:

Current

FRDC Expenditure:

$328,743.00

Program(s):

Environment, Industry

Need

Annual estimates of SBT spawning stock abundance are required to assess the status and productivity of the stock. Prior to the original CKMR study, there was no direct index of abundance of the spawning population The majority of the difference in the estimates of spawning stock status between the 2011 and 2014 stock assessments was due to the influence of the CKMR data, in combination with the 1990’s conventional tagging data. This reduced the overall uncertainty in spawning biomass and natural mortality and, therefore, identified a number of unproductive (pessimistic) parameter combinations as implausible. These were removed from the reference set of OMs (Anon 2014) The schedule of implementation of the CCSBT MP includes a full stock assessment is scheduled for 2017. As a result of decisions by CCSBT to discontinue the Aerial Survey and move to gene-tagging, the CCSBT will initiate development of a new MP in 2017. Candidate MPs will be tested (in 2018) and a final MP selected using the OMs reconditioned in 2017 as part of the full stock assessment. The aim of this FRDC project is to provide a time-series of absolute abundance estimates of spawning potential from 2002 to 2013 for direct use in the CCSBT OMs. This abundance trajectory of the spawning potential of the stock will be independent of CPUE and catch data from the main fisheries, and will be an important input to domestic and international consideration of the stock status and performance of the rebuilding plan. If the CKMR information is not available for the 2017 assessment, it is highly unlikely to be incorporated for testing of Candidate MPs. This would mean the CCSBT MP used to recommend future global TACs would not be “calibrated” with the most recent information on the status and recent trend in the spawning stock.

Objectives

1. Process archived tissue samples, extract DNA and genotype (~16,000 individuals, 2006-2014)

2. Combine genotypes from 1 with those from related CCSBT project (2015-2016)

3. Estimate time series of total adult abundance, spawning potential and total mortality on the spawning population

4. Report outcomes to SBTMAC, AFMA and CCSBT Scientific Committee for incorporation into 2017 update of the CCSBT Operating Model.