Scientist Goro Yoshizaki is confident in being able to breed tuna from mackerel in the years to come. (Photo: soi.wide.ad.jp, G. Yoshizaki)
Mackerel could save tuna from extinction
Monday, June 14, 2010, 23:30 (GMT + 9)
Researchers are using mackerel in an effort to breed Atlantic bluefin tuna and boost its populations.
In the wild, female tuna release hundreds of thousands of eggs each spawning season, but almost zero eggs reach maturity.
If mackerel raised in captivity for about 12 months can be manipulated to lay tuna eggs, tuna fry could be acquired cheaply and abundantly.
The technology could be used in aquaculture and, more importantly, if these fry were released back into the ocean, depleted wild tuna stocks could recover and save the species from extinction, Asahi Shimbun reports.
"We're just using the mackerel as a surrogate, so to speak. The resulting fry are 100 per cent genuine bluefin tuna," told Goro Yoshizaki, an associate professor of aquatic bioscience at Tokyo University of Marine Science and Technology who has been researching the topic for almost 12 years.
Germ cells are the early stage stem cell of sperm and eggs and exist in both male and female adult tuna. If it becomes possible to transplant these cells into mackerel, the female mackerel's ovary could produce tuna eggs and the male mackerel's testes could produce tuna sperm.
Then, if these male and female mackerel find each other and spawn, they will generate tuna fry.
"We have found that if the transplant is performed on newly hatched fish, the rejection of foreign cells rarely occurs," Yoshizaki said.
If the male and female tuna germ cells are transplanted into mackerel while these are still very young, the animals will mature to produce tuna sperm or eggs per their gender.
The cells are transplanted after sterility measures are taken, to ascertain that the mackerel do not produce mackerel eggs or sperm and can only produce tuna eggs or sperm henceforth.
"This high degree of flexibility has been present in fish reproductive cells right from the beginning," he commented.
Yoshizaki and his colleagues’ exciting discoveries were published in a US scientific journal in 2006.
In 2003, Yoshizaki was able to get land-locked salmon to produce rainbow trout eggs and sperm. Since 2005, he has been trying to replicate the accomplishment using mackerel and tuna.
In September 2009, he got implanted tuna germ cells to take hold inside a mackerel. Yoshizaki is now trying to use the mackerel to spawn tuna.
"In another seven or eight years, I believe we'll be able to breed tuna from mackerel in a stable manner," he affirmed.
The spawned tuna fry can be artificially raised to maturity through aquaculture or be released into the wild and mature naturally.
"We aren't employing any complicated techniques such as gene manipulation," Yoshizaki said. "Just as with the stocking of salmon, we only need to increase tuna numbers to equal the amount that is harvested by man."
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By Natalia Real