4 results
Environment
PROJECT NUMBER • 2003-002
PROJECT STATUS:
COMPLETED

Spatial interactions among juvenile southern bluefin tuna at the global scale: a large scale archival tag experiment

Results have increased our confidence in the recruitment index based on the aerial survey in the Great Australian Bight (GAB) by confirming that the timing and duration are ideal, that the majority of juvenile SBT are likely to return to the GAB each summer, and that based on current evidence it is...
ORGANISATION:
CSIRO Oceans and Atmosphere Hobart
TAGS
Wild Catch
SPECIES
Southern Bluefin Tuna

Developing a management procedure based recovery plan for southern bluefin tuna

Project number: 2011-034
Project Status:
Completed
Budget expenditure: $160,000.00
Principal Investigator: Richard Hillary
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 19 Dec 2010 - 29 Sep 2011
:
TAGS
Stock Assessment
Innovation
Fisheries Management
SPECIES
Southern Bluefin Tuna

Need

There is an immediate and strategic need for the CCSBT to agree to an MP to guide the global catch setting to ensure the rebuilding of the SBT stock. For this to occur, an MP needs to be developed and agreed by the CCSBT; failure to do so will result in the global catch of SBT being reduced to 5000-6000 t, with a subsequent significant impact on the Australian SBT fishery. Australia in collaboration with Japanese and other CCSBT member scientists are responsible for the development and evaluation of the MP, which in the context of a Regional Fisheries Management Organisation (RFMO), such as CCSBT, is a unique and innovative concept that will establish a rebuilding pathway for the stock. Having a rebuilding strategy that has been rigorously and openly tested, is robust to the key fishery-specific issues and uncertainties, and establishes a process whereby decisions will be made and enforced will be a first in the tuna RFMO milieu.

As an effective recovery plan for SBT can only exist at the international level (given the shared nature of the resource) the development and adoption of the MP work can also be interpreted as a direct requirement of the current conservation dependent status of the stock. It is therefore essential to complete the MP development work for adoption by the Commission in 2011.

Objectives

1. Development of candidate management procedures, within the CCSBT international collaborative scientific structure, to guide the recovery of Southern bluefin tuna
2. Define and compute a set of reference points for evaluating the performance of the MPs and the risk status of the stock that are consistent with both the rebuilding criteria and the underlying models used to evaluate the MPs themselves

Improved fishery independent estimates of southern bluefin tuna recruitment through integration of environmental, archival tag and aerial survey data

Project number: 1999-105
Project Status:
Completed
Budget expenditure: $139,674.52
Principal Investigator: Alistair Hobday
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 6 Sep 1999 - 30 Nov 2003
:
TAGS
Tagging
Survey
Stock Assessment
Stakeholder
Reproduction
SPECIES
Southern Bluefin Tuna

Need

The parental biomass of SBT remains at historically low levels, there is evidence from CPUE and VPA analyses that recruitment has continued to fall throughout the 1990’s, and there is significant disagreement within the CCSBT Scientific Committee on the prediction of population levels into the future.

It is therefore essential to know more about the recruitment dynamics of SBT, and in particular to reduce the uncertainty in the aerial survey estimates of surface abundance of juveniles in the GAB. These remain the only fishery independent source of abundance data on SBT, and as such their importance cannot be overstated.

To reduce the uncertainty in the current aerial survey estimates we need to investigate how environmental factors and surfacing behaviour influences what is seen during the surveys. If the current levels of uncertainty in the indices are reduced by incorporating these sources of variation into the indices, the value of the indices to the CCSBT will be substantially increased.

There is large variation in estimated surface abundance between survey replicates within a season and between seasons but there are also large differences between years in environmental conditions in the GAB (eg sea surface temperature), which confound the interpretation of changes in the index between years. It is possible that the apparent decline in surface abundance over the last 6 years is due to environmental and behavioural variation rather than indicating a true decline in the global abundance of juvenile SBT.

To adequately understand how environmental variation and the resulting behavioural responses of SBT affect the recruitment indices we require thorough analyses of:
1 the surfacing behaviour in SBT and its relationship with environmental variables, migration patterns and possibly also feeding behaviour,
2 the relationship between surface abundance (ie. what the aerial survey detects) and environmental variables,
3 the spatial variation in abundance of SBT in the GAB (incorporating both data on surface abundance from the aerial survey and data from archival and conventional tagging experiments).

The proposed project will use all existing data, collected over almost a decade, with funding from industry, FRDC, CSIRO and Japan. These data are an invaluable resource. The integration of behavioural, environmental and abundance data into an improved estimate of the surface abundance of SBT is listed under Priority 2 and 3 of STBMAC Research Priorities.

Objectives

1. To conduct a range of statistical analyses of data from the archival tags and environmental and oceanographic archives to determine whether there are common responses in surfacing behaviour to environmental conditions through space and time
2. To conduct a range of statistical analyses of aerial survey data on surface distribution and surface abundance of juvenile SBT, and environmental and oceanographic archives to develop a spatial model of abundance which allows for environmental variation through space and time. This would include analyses of how environmental conditions affect the detectability of surface schools from planes.
3. To develop an integrated analysis of abundance of SBT in the GAB incorporating the surfacing behaviour, surface abundance and spatial distribution models developed above.

Final report

ISBN: 1-876996-41-2
Author: Alistair Hobday
Final Report • 2003-11-24 • 9.54 MB
1999-105-DLD.pdf

Project products

Workshop
1999-105-Product-Report of the Aerial Survey Workshop 14 February 2000 Port Lincoln

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
Project Status:
Completed
Budget expenditure: $328,743.00
Principal Investigator: Campbell Davies
Organisation: CSIRO Oceans and Atmosphere Hobart
Project start/end date: 2 Oct 2016 - 29 Apr 2018
:
TAGS
Stock Assessment
Reproduction
Rac Cmwth
Mortality
Modelling
SPECIES
Southern Bluefin Tuna

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.

Final report

ISBN: 978-1-925994-04-9
Author: Campbell Davies
Final Report • 2020-06-16 • 3.04 MB
2016-044-DLD.pdf

Summary

This report presents the results of the first application of Close-Kin Mark-Recapture (CKMR) using both Parent-Offspring Pairs (POP) and Half-sibling Pairs (HSP). This application to Southern Bluefin Tuna (SBT) has been successful, providing a decadal time series of absolute abundance, total mortality and selectivity of adults. The method and the results have been reviewed and accepted by the Scientific Committee of the Commission for the Conservation of

Project products

Film/Video • 2020-06-16

Summary

This research has provided the world’s first scientifically tested management procedure for Southern Blue Fin Tuna (SBT) using DNA sequencing and genetic tagging to manage stock levels and deliver significant economic benefits.
Resource list • 2020-06-16 • 82.79 KB
papers 2016-044.pdf

Summary

The following working papers from this project were submitted to the CCSBT
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