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Survival of the speciesTuna breeders adapt new methods
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승인 2010.02.16  12:10:01
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▲ Jeju fish farmers are utilizing a new net system that they believe could help save fisheries stock. Photo courtesy National Fisheries Research and Development Institute


The Commission for the Conservation of Southern Bluefin Tuna reports that the reproduction rate of Southern bluefin tuna is only 5 percent of the original spawning stock. According to the commission’s Web site, bluefin are found throughout the southern hemisphere mainly in waters between 30 and 50 degrees south, but only rarely in the eastern Pacific.

However, Jeju Fisheries Research Institute officials say the number of bluefin is increasing in Jeju waters, and comparatively so too is the number of fishing boats. There is, however, no official figure on the number of bluefin tuna in Jeju waters, nor of the amount being caught. Some scientists around the world fear that if bluefin tuna fishing does not cease entirely, in a few years there will be none left to catch. Ji Seung Chul, a researcher at the Jeju Fisheries Research Institute, said the bluefin fishery should remain viable as long as those involved are aware of the species’ delicate state and begin to take preventative measures - which is what he and others involved in new methods of breeding bluefin in Jeju are doing.

“My future plan is that fishermen will no longer need to catch tuna, instead their needs can be met by breeding suppliers,” Ji said. “I would like for bluefin breeding to become a major industry in Jeju,” Success, he believes, would mean being able to balance the number of tuna caught in its natural habitat by replenishing the waters with farm-raised tuna, which would become a major source for commercial sales.

Until October 2009, Ji said, no one in the world had used the type of breeding system Jeju utilizes now. Traditionally, the system for breeding bluefin has revolved around the use of surface nets, leaving both fish and equipment exposed to the elements. A typhoon or severe storm could potentially destroy an entire breeding effort.

If a surface net system is damaged there is risk of a large monetary loss as well as health risks to fish outside of the breeding net. Ji said fish cannot survive within a 15 meter radius of the surface net because of the stagnant water surrounding it. The nets prevent water movement, which in turn causes the water to become inactive with excess excrement and other pollutants. The supplements given to the tuna within the surface net systems also weaken the fish’s natural immunity and many of the fish become diseased. If these nets are damaged during a storm then fish carrying transmittable diseases could come in contact with fish outside of the net and spread the disease.

“Our system however is fully immersed, Ji said. “It is the first in the world to involve a system entirely under water. This way, the fish are safe from the elements. Not to mention that the system has minimal environmental impact.” The submerged offshore net cage was first used in 2005, but only applied to tuna a little more than three months ago. Ji credited the success so far had with breeding tuna to testing for the past few years on mackerel and other fish similar in migratory patterns.

Park Jin Woo is also preparing to start “farming mother tuna” with the Korean Ocean Research and Development Institute. “Right now the majority of tuna caught in Jeju seas are bluefin, which are known to be the most expensive, the most delicious and the biggest, growing up to 800 kilograms,” he said.

The key locations, according to Park, for catching bluefin are Pyoseon, Seogwipo City and Hwasun, Andeok. Tuna sells for between 35,000 won and 40,000 won per kilogram, Park said. “Compared to other fish businesses, tuna is fairly lucrative.”

He said that the amount of tuna harvesting done in the future needs to be regulated. “The increase in the amount of tuna fishing means the success of tuna farming. That is, mother tuna lay eggs, and we grow them and sell. I think it will be possible within the next seven years. If it comes true, there is no other concern regarding tuna fishing,” he said.

The Commission for the Conservation of Southern Bluefin Tuna decided during its annual meeting in October to decrease the global bluefin total allowable catch for the 2010 and 2011 fishing seasons by 20 percent.

Han Jung Ho is management support division director of Noah Net Technology Systems, one of the lead developers in the production of submerged netting. He said that the best thing that could be done to save bluefin tuna is to cease fishing the species completely. However, regulation is difficult, he said, and it is important to consider alternatives. He, like the other tuna breeders, believes the answer lies in the hatching technology.


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