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Spanish Researchers Close To Reproducing Bluefin Tuna In Farms

Scientific Researchers from the Spanish Institute of Oceanography (IEO) have succeeded, for the first time, in the production of several million viable eggs of bluefin tuna in captivity by means of hormonal induction. This opens the door to the possibility of reproducing this highly appreciated species in sustainable farms.

Never before had such large quantities of eggs from females of Atlantic bluefin tuna in captivity been successfully fertilized, according to researcher Fernando de la Gándara, who is the coordinator of this European project called SELFDOTT, led by the IEO, involving thirteen partners from nine countries.

The IEO has obtained more than five million of fertilized eggs of bluefin tuna in the facilities of The Gorguel near Cartagena, a site run by Tuna Graso, belonging to the Ricardo Fuentes group.

Obtaining viable eggs of bluefin tuna from the fish in captivity is the first step towards the production of this species without necessarily resorting to depleting the natural stocks and thus supplying the market sustainably in the future, according to scientists.
Researcher De la Gándara indicated that female bluefin tuna in captivity are affected by a kind of stress, probably caused by being caged, which hinders the final stage of reproduction. This stress hampers the ejection of the mature egg, which is the initial step for subsequent fertilization, in the water, in contact with the male’s sperm.

However, this problem has been finally resolved with the improvement of the hormone treatment introduced into the tuna.
Moreover, the living conditions of the tuna in cages has also been enhanced, as well as the improvement of the collecting  techniques of the one millimeter diameter sized eggs, with very promising results for future captive breeding of this species, according to experts.

The hormone treatment is implanted in the female tuna by small harpoons fired by sea divers in the, thus facilitating the expulsion of the mature egg. In the case of the male tuna, this same treatment activates their sperm.

The research has been performed on bluefin tuna of around 90 kilograms and 1.5 meters in length.

The time elapsed between the hormone induction to stimulate the egg expulsion and the actual ejection is of about 72 hours.