In DepthAnimal Health

Unplanned experiment could help save a key farmed fish

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Science  06 Mar 2020:
Vol. 367, Issue 6482, pp. 1064
DOI: 10.1126/science.367.6482.1064

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An emerging virus has been killing farmed tilapia in Asia, Africa, and the Americas. There's no cure and no vaccine, and the virus is likely spreading, threatening one of the world's most important farmed fish. New findings, however, are providing hope that Nile tilapia (Oreochromis niloticus), the most common kind of farmed tilapia, could be bred to resist the virus. In 2018, the virus struck a pond at WorldFish, a publicly funded international research center, which helped researchers identify genetic variants with high survival rates. About 50% of the variation in survival was due to genetics, an encouraging figure for breeding resistance to the virus. The researchers also found that bigger—and more valuable—fish were just as likely to resist the disease as the smaller fish. That finding suggests breeders won't have to sacrifice yield to boost resistance. Still, getting resistant tilapia into the world's ponds could take years. Researchers need a genomic test that would allow breeders to quickly identify fish with desirable genes, and they need a reliable and realistic way to infect the fish to find out whether they really are resistant. Mass-producing the fish in hatcheries and distributing them— especially in the developing world—will be a tall order.

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