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Output Of Farms Fattening Wild Tuna Keeps Reducing

While the global farmed fish market continues to rise, the farmed tuna volume falls considerably behind. With the market relying almost entirely on the capture of wild tuna to fatten in captivity, bluefin stocks plummet to highly depleted levels during the last decade.

In 2011, while global farmed fish production reached huge heights of around 60 million tons, farmed tuna did not even account for one percent of this total. Similarly, the 5,554 tons of farmed tuna that year was less than one percent of the figure of wild tuna catches.

However, tuna farming has become a huge focus in terms of the bluefin species, a prized tuna fish that has remained in an overfished state for many years due to the over exploitation of its stocks. Its high demand in the Japanese sushi and sashimi market has meant for over 40 years Japanese scientists have carried out extensive research into the spawning of tuna in captivity.

The dramatic escalation in the volume of farmed tuna which took place in 2007 is thought to have been due to the addition of seven more Mediterranean countries involved in bluefin tuna farming, taking the total to 11, driven by the huge amounts this highly desired fish could be sold for. But the collapse in catches, combined with the threat to future stocks becoming increasingly concerning, and governments and RFMO’s imposing catch reduction measures,  fattening of bluefin tuna  in farms has recently significantly decreased.

But for many years, environmental groups such as Greenpeace and the World Wildlife Fund (WWF) have battled against bluefin farming methods, believing that high demand for this tuna species from countries like Japan has caused a sharp decline in the numbers of tuna left in the oceans. In a bid to capitalize on these markets, bluefin tuna were being caught well above sustainable levels and taken to feeding ranches in order to increase their weight before being sold on at weights of up to 70 kg.  Stringent catch measures taken in recent years seem to have its effect and the first signs of recovery of bluefin stocks are appearing.

Some scientists are also fearful that fattening tuna is harming the world’s oceans more than helping. A chief scientist from Oceana said: “We’ve seen all of the problems associated with farm-raising salmon, and there’s no question in my mind that the problems with bluefin tuna are just as large,” outlining that the practice of catching other small wild ocean fish to feed captive bluefin tuna means those fish are no longer available to other predators. “We’re essentially robbing the ocean ecosystem of key food items for other species and diverting them to bluefin tuna.”

Last year saw tough restrictions imposed on the domestic fattening of juvenile bluefin tuna, with the Japanese government being ruled by the Fisheries Ministry to create regulations to stop such high volumes of young bluefin being caught in the ocean to rear in captivity, before getting the chance to lay eggs and therefore resulting in further depleted stocks of the high demand fish.

The European Commission launched a project called SELFDOTT (Self-sustained Aquaculture and Domestication of Bluefin Tuna) that has succeeded in breeding Atlantic bluefin in floating cages without the use of hormones. So far however, tuna farmers have not yet been able to make the closing of  the cycle of bluefin tuna commercially successful,  with the larvae from the eggs only growing to just over 1kg in 3 months.

While it is expected that the consumption of farmed fish may surpass those caught in the wild this year, figures show this is most unlikely to happen with tuna any time soon. Sustained efforts into the captive rearing of bluefin tuna hope to push the total of farmed tuna up without further depleting the oceans wild stocks, however its success will depend on the possibilities to make it commercially viable, and environmentally acceptable.