OCEANS AND ATMOSPHERE

Southern Bluefin Tuna Gene-Tagging Program
The gene-tagging program is a new approach for monitoring absolute abundance of juvenile Southern Bluefin Tuna (SBT). It uses the unique genetic fingerprint of a fish to identify if a ‘tagged’ fish is recaptured. Gene-tagging resolves tag reporting rate issues in conventional tagging programs and is a fishery-independent alternative to catch-per- unit-effort indices.

The abundance estimates will be used in stock assessment models and is essential for a new management procedure to calculate the recommended global catch of SBT. The Commission for the Conservation of Southern Bluefin Tuna has funded an on-going gene-tagging program for recruitment monitoring of SBT.

DNA identifies tagged & recaptured fish
A small tissue sample is collected from fish (“tagging”) and the fish is released alive to mix with population. The unique genetic DNA fingerprint is the ‘tag’.
A second set of samples is collected, 1 year later, during commercial harvesting of fish*.
A multi-disciplinary team at CSIRO O&A developed tissue sampling tools and the set of genetic markers for reliable individual identification.

Key Advantages
The data are fishery independent;
No reporting rate issues; it is invisible, lasts forever, there is no tag shedding; and no tag rewards.

Pilot project verifies feasibility & logistics
The pilot program has demonstrated: high-throughput DNA extraction and cost-effective genotyping; and has delivered an estimate of abundance of juveniles.
20,000 fish tissue sampled each year

For further information contact:
CSIRO Oceans and Atmosphere
Ann Preece
e  ann.preece@csiro.au
t  +61 3 6232 5222

First abundance estimate: 2.4 million 2 year old fish (similar to 2017 stock assessment models median estimate: 2.1 million)

Acknowledgements: * Australian SBT Industry members provided access to fish & facilities during commercial harvesting.   CCSBT, CSIRO and EU funded.