Share via Email This article is over 5 years old The latest data from the international scientific committee which monitors tuna in the Pacific showed bluefin tuna stocks were a small fraction of what they had been and were in danger of all but disappearing. But the advent of industrial fishing methods and a taste for the species among rich sushi devotees have led to its being hunted to the brink of extinction.
Southern Bluefin Tuna Thunnus maccoyii are majestic, temperate ocean dwellers, roaming across the oceans of the southern hemisphere, from the tropics to the sub-Antarctic. They grow to two metres and kilograms, mature between eight and 20 years of age, and can live to Southern Bluefin eggs are spawned in warm waters off Java and north-western Australia.
As larvae and small juveniles they ride the Leeuwin Current down the coast of Western Australia to spend their first summer in south-western WA and the Great Australian Bight. They continue to summer in the Bight, wintering in either the south-east Indian Ocean or Tasman Sea until about five.
Then they stop returning to the Bight. Instead they move between feeding grounds, areas of high productivity spread between New Zealand and South Africa. Later as mature adults they join the spawning migration to the tropics below Indonesia.
Status Southern Bluefin are highly prized on the Japanese sashimi market, where the overwhelming majority of the global catch is sold. They have been heavily fished since the s by high-seas long-line vessels and purse seine. They have also been grown in pens in Port Lincoln South Australia since the s.
This is well below accepted national and international sustainable levels. Threats Overfishing is the greatest recognised threat to Southern Bluefin. With low numbers of spawning adults, natural variation means there is a high risk of further declines.
Several years of low juvenile survival, even with little or no change in fishing, can result in rapid decline. There is no buffer of long-lived adults that exists when populations are higher.
Management of Southern Bluefin is via international agreements on quotas, which can often lead to decision paralysis and status quo management. This management system can be slow to respond to problem signals such as low numbers, leaving the population ill-equipped to deal with the vagaries of juvenile survival.
Inthe revelation of significant under-reporting of catches from the long-line vessels further increased the uncertainty in stock status and the risk of future tuna declines.
An international body of major fishing nations, the CCSBT renewed its commitment to developing a formal rebuilding plan for the Southern Bluefin.
Monitoring of the population has shown that the initial quota reductions have stopped the overfishing. Strategy Member scientists of CCSBT instigated a process of developing a robust rebuilding strategy in the early s.
This strategy, called a Management Procedure, differs to more common and problematic ad hoc quotas. The specific objectives to be achieved are agreed beforehand. Quota setting decisions are largely automatic - key data is fed into the procedure and a total allowable catch is produced.
No negotiation is permitted and no lengthy stock assessment process is required. Stakeholders can be satisfied the procedure will rebuild stock under a wide range of potential future conditions.
This is the first such outcome for an international tuna fishery. Conclusion An important benefit of the Management Procedure approach is that it gives scientists more time to explore the remaining uncertainties in our understanding of the Southern Bluefin.
CSIRO scientists have recently completed electronic tagging and genetic abundance estimation projects to better understand the migration patterns and breeding capacity of the stock. It is expected that, even with the rebuilding strategy in place, recovery of the tuna will take a number of years.
Southern Bluefin are long-lived and mature late, so the implementation of the Management Procedure is the start of a process, not the conclusion of one.
The next challenges for Southern Bluefin are for members of the CCSBT to maintain the accurate reporting of data from the fishery, to ensure that recommendations coming from the Management Procedure are adhered to, and for the scientists to continue integrating the latest research into the management framework so that future decisions are made on the best available scientific advice.
The Conversation is running a series on Australian endangered species.Jun 04, · To get a good understanding of how overfishing of the bluefin tuna affects the environment, other organisms, and humans, we must first take a look at the food web to which the bluefin tuna belongs.
The southern bluefin tuna is a part of the marine food leslutinsduphoenix.com: Andrew. Five out of the eight tuna species are at risk of extinction due to overfishing, according to conservationists.
Such overfishing has severely damaged bluefin stocks. According to the WWF, managed to breed Southern Bluefin Tuna in captivity and was awarded the second place in World's Best Invention of by Time magazine.
As food The fresh or frozen flesh of tuna is widely regarded as a delicacy in most areas where it is shipped, being . The southern bluefin tuna has long inhabited the warm waters of the Pacific, Atlantic, and Indian Oceans.
In the past 50 years, the population has been devastated by overfishing, which wiped out nearly 85% of southern bluefin tuna in the world. The fish has been considered a delicacy in Japan as far back as years ago.
Overfishing is the greatest recognised threat to Southern Bluefin. With low numbers of spawning adults, natural variation means there is a high risk of further declines. Overfishing of the Southern Bluefin Tuna and Current State of Fish Stocks.
Available stocks of Southern Bluefin Tuna have decreased rapidly in the past half century and today current populations face continued threat of over exploitation.