Aquaculture for all

Closed Cycle Bluefin Tuna: New Opportunities Are Born

Water quality Sustainability Breeding & genetics +8 more

Aquaculture history has been made with the announcement that Southern Bluefin Tuna have been successfully spawned in captivity for the first time ever, writes Adam Anson, TheFishSite.

"Our billion dollar babies"
Photo: Clean Seas

Tens of millions of tuna eggs were produced in the Arno Bay facility in Port Licoln, South Australia. To put the size of this achievement into perspective, a professor, who worked on the project, said that even if only a small percentage of the larvae survived the number of captive tuna would still exceed all those in the entire history of Australian aquaculture.

Clean Seas Tuna, the company behind the research says that this is a revolution of tuna, which could lead to the creation of a new multibillion dollar industry. Much like salmon aquaculture that has gone before it, the tuna industry may change irreversibly.

Currently, all tuna start life in the sea. Around the globe their stocks are in dramatic decline, but the bluefin tuna -- the largest and most spectacular of them all -- is in the most amount of trouble. At 60km/h they may be extraordinarily fast, but they are not fast enough. High-tech fleets have forced the numbers down by almost 90 per cent in many areas.

To reconcile this situation the International Commission has set catch quotas appropriate for the survival of current stocks. However, according to Oceana, the largest international group dedicated to protecting the world's oceans, these are nearly impossible to enforce. Some conservationists estimate that the fishing industry took 50,000 metric tonnes of bluefin from the mediterranean by mid June of 2008. The quota was set at 28,500 tonnes.

Data compiled by the World Wildlife Fund (WWF) points to patterns of decline that will see the Mediterranean bluefin being completely wiped out in just three years time if fisheries managers and decision makers keep ignoring the warnings from scientists. Dr Sergi Tudela, Head of Fisheries at WWF Mediterranean says: "the WWF has no choice but to again urge the immediate closure of this fishery."

But whilst the long term consequences are dramatic, the short term gains are considered by many in the industry to be far greater. It may be difficult to comprehend, but the size and value of the Japanese industry -- the insatiable demand at the heart of the 52 acre Tsukiji market -- is almost single-handedly driving the destruction of the bluefin.

Here, a single bluefin can reach prices upwards of $100,000. The fish, prized for its buttery belly meat, will then be taken away, chopped down in restaurants and resold as sushi and sashimi. In the end its value can exceed $1,000,000. As the value of bluefin remains so high, so the fleets will keep fishing, so the stocks decline, and so the demand increases. The value of the bluefin will keep rising and unless something is done, this downward spiral will take the bluefin to extinction. Yet this latest step in farmed production offers a faint glimmer of hope for the bluefin. If appetite can be satisfied without inflicting harm upon wild stocks then the bluefin may yet escape the cycle. Farming bluefin could theoretically meet all global demands whilst creating huge economic gains for those within the industry, but like all things, if the answer seems to be just a little too easy, most likely it is.

The History of Conflict and a New Way Forward

Bluefin has been farmed for many years, but whilst operations may have been economically successful, they have also been hugely unsustainable. To appreciate the problem, you have to appreciate the bluefin and the lives they lead in the ocean.

"Recreating the natural breeding cycle of one of the world’s premier pelagic fish species was a key step towards ensuring sustainability of this key species"
Clean Seas chairman, Hagen Stehr.

Bluefin are complex, intelligent fish. Scientists that work with them often cite how they are in awe of their subjects. These mysterious, warmblooded giants swim deep beneath the waves where they can grow to be 12 feet in length and weigh upwards of 1,500 pounds. Said to be the most highly evolved fish on Earth, the bluefin undertakes epic trans-Atlantic migrations of up to 4,800 miles (7,700 km). A single female bluefin can produce up to 30 million eggs each spawning season, but it is getting them to breed at all which has eluded scientists.

Not only is it difficult to replicate anything similar to their vast migrations, but it is also difficult to simulate other specific conditions, which they require to remain stress free. Tuna are sensitive to daylight, to water quality, to bacteria, viruses and parasites and also to temperature. It has proved impossible to simulate all the right conditions, and so whatever events and signals that trigger breeding in the wild are lost in captivity.

If you cannot produce juvenile tuna in farms, one solution is to take them from the ocean and then fatten them in net pens. This process is known as 'fattening', or 'ranching'. An enormous fortune has been made by ranching hundreds of thousands of bluefin in this manner in the Mediterranean. Due to the success, this process now occurs in Mexico, Canada, Australia and Japan. It can take months for juvenile tuna to reach maturity and throughout this time these carnivores consume 20 kilogrammes (44 pounds) of smaller fish for every kilogramme (two pounds) that they put on. With all fish stocks in decline across the entire ocean, fattening bluefin in this manner is clearly not a sustainable practice, but for wild bluefin stocks it is even more detrimental, cutting off a new generation before they have chance to breed.

It has long been acknowledged that any attempt to sustain bluefin stocks must involve replicating them in captivity. Now, thanks to Clean Seas, the life-cycle of Southern Bluefin Tuna is complete. According to the company, they have achieved continuous spawning by its captive Southern Bluefin Tuna broodstock over 35 days; production of more than 50 million fertilised SBT eggs and 30 million larvae; fertilisation of more than 90 per cent of eggs; production of fingerlings, which grew to about 2.5 cm in about 28 days; and significant advances in knowledge required for the production and commercialisation of SBT as a sustainable resource. Clean Seas say that they now have enough eggs and larvae to produce tuna for the next 18 years. They plan to establish a valuable SBT sperm bank and secure sustainable production. The success of the hatching means the company expects to reach its ultimate goal of commercialisation of fingerlings this year.

Because of the nature of the intellectual property supporting this achievement, no further technical detail about the Southern Bluefin Tuna breeding programme is currently available. However, according to other press reports, researchers from Germany’s Heinrich Heine University used spearguns to deliver reproductive hormones to caged bluefins off Italy; within days, the fish spawned millions of fertilised eggs. According to Mother Nature Network, the team hypothesized that when the fish are in captivity, a key hormone used in bluefin reproduction, gonadotroptin-releasing hormone (GnRH), isn’t produced or malfunctions. So the researchers created a synthetic version of GnRH, inserted it in a biodegradable device that slowly releases the substance over a period of time, and implanted it into adult bluefin.

"From a global perspective, successfully recreating the natural breeding cycle of one of the world’s premier pelagic fish species was a key step towards ensuring sustainability of this key species at a time when wild stocks are under significant pressure," said Clean Seas chairman, Hagen Stehr.

However, many challenges still lie in wait, such as the issue of sustainably feeding these fish, whilst dealing with the many environmental repercussions that have had severe effects on other aquaculture operations. Fortunately, not only are Clean Seas the first to breed captive Southern bluefin, but they are also the first aquaculture company in the Southern Hemisphere to earn the internationally recognised sustainability accreditation and logo mark of the Friend of the Sea organisation, accredited to them for the production of Hiramasa Kingfish and Suzuki Mulloway in Port Lincoln.

Whilst the future of the bluefin has opened up in a new direction, the journey must be taken one step at a time with careful management and the emergence of a new set of global bluefin aquaculture standards. Just as the cycle seemed set to eradicate bluefin, so the potential for its survival materialises.

May 2009