Just as people in Japan had begun to resign themselves to the idea that eating coveted fatty tuna may soon no longer be possible, mackerel has appeared as an unexpected savior.
The background to this was a proposal to ban international trade in Atlantic bluefin tuna. The proposal was defeated at the recent meeting of parties to the Convention of International Trade on Endangered Species (CITES), but it could be reactivated at any time.
It turns out there may be a way to bolster the tuna population by using mackerel to breed the much sought-after fish.
Though female tuna release hundreds of thousands of eggs at each spawning, the number that reaches maturity in the wild is close to zero. However, if mackerel raised in captivity for about a year can be made to lay tuna eggs, tuna fry could be obtained inexpensively and in large amounts.
This would not only be useful for aquaculture, if the fry were released back into the ocean, but overfished wild tuna could be saved from extinction as well.
So, is it really possible for mackerel to produce the eggs of a tuna? And even if it is, wouldn't the result be some kind of bizarre tuna-mackerel hybrid?
"It's not a problem. We're just using the mackerel as a surrogate, so to speak. The resulting fry are 100-percent genuine bluefin tuna," explained a grinning Goro Yoshizaki, 44, an associate professor of aquatic bioscience at Tokyo University of Marine Science and Technology who has been researching the subject for close to 12 years.
Germ cells--the early stage stem cell of sperm and eggs--are present in male and female adult tuna. If the cells can be transplanted into the mackerel and they take hold, the female mackerel's ovary will produce tuna eggs while the male mackerel's testes will produce tuna sperm. Should these male and female mackerel meet and duly spawn, tuna fry will be the end result.
