SOUTHERN BLUEFIN TUNA
Australia’s aquaculture production of tuna consists solely of ranched Southern Bluefin Tuna (Thunnus maccoyii) from South Australia. It is the second largest contributor by value and volume to Australia’s aquaculture sector (behind salmon).
The birth of the Southern Bluefin Tuna (SBT) ranching industry in 1991 saw fishermen move from polling and netting fish straight from the wild, to live capture of wild fish for fattening prior to harvest. Incorporating aspects of both wild-capture and aquaculture, the Southern Bluefin Tuna industry is now one of the most important seafood sectors to the export market, with 90% of product heading overseas (mostly to the Japanese sashimi market). More than 95% of Australia’s total catch of Southern Bluefin Tuna is taken through ranching, with the remaining 5% taken on long-lines.
In Australia, SBT are classified as ‘Conservation Dependent’ and managed under a species recovery plan. This means fishing can still occur, but the amount caught is limited by a total allowable catch (TAC). The international Commission for the Conservation of Southern Bluefin Tuna (CCSBT) set the global TAC low enough to enable stock recovery and long term sustainability.
The ranching process involves the capture of live tuna at around 18kg (average) in the Great Australian Bight using purse seine methods. Vessels operate between December and March under strict regulations imposed by the Australian Fisheries Management Authority (AFMA). The fish are transferred through underwater ‘gates’ between nets into specialised tow pontoons. The fish are then slowly towed back to lower Spencer Gulf near Port Lincoln, where they are transferred to static ranching pontoons. Animals are fattened for 3-8 months on a diet consisting mainly of locally caught sardines.
Tuna harvest occurs in the cooler months, peaking in June/July. The majority of SBT are shipped frozen (-60°C) directly to Japan.
In 2017, Southern Bluefin Tuna ranching was conducted by 8 different companies in the Lincoln Offshore Aquaculture Zone. The total value of the fishery is AU $150 million, generating crucial employment and flow-on benefits in South Australia’s regional communities.
In past years there has been significant progress in the development of aquaculture-bred Southern Bluefin Tuna, including the establishment of on-shore breeding facilities. Clean Seas suspended their SBT breeding program in 2013, with plans to re-engage the research in the near future.