Cultivating stronger salmon species is a "top priority"

Original title: Cultivating stronger salmon species bes a "top priority
About a decade ago, thyfish farmed on Israeli farms began to mysteriously die. The fish's skin festers and is accompanied by internal bleeding. Sometimes, ponds full of fish are wiped out. In 2014, researchers identified the culprit: a previously unknown virus they named erythra. Since then, the virus has been found on farms in Asia, Africa and the Americas. There is no cure, no vaccine, and the virus is likely to spread, threatening one of the world's most important farmed fish. "This is a major global problem," said John Benzie, a geneticist at WorldFish, an international publicly funded research center.
, however, the new findings offer hope for the development of antiviral species of Nile clockers, the most common cultured viruses. Benzie and his colleagues reported last month in the journal Aquaculture that in 2018, the virus hit a pond in WorldFish, where there are many thyroids used in breeding experiments, and fortunately some fish have been shown to be completely resistant to the virus. "This is good news for rye fisheries," said Morten Rye, a fish geneticist at Benchmark Genetics, which breeds rye and other aquaculture species.
is the second most popular fish in aquaculture, after carp. Farmers in more than 120 countries currently catch about 6 million tons of erythra per year. This is particularly important in developing countries, many of which rely on high-end products first developed by WorldFish in the 1990s.
the emerging virus affected several cultured thyfish and may have caused problems for at least a few years before it was discovered. Although researchers know that some areas have been hit hard, the overall distribution and impact of the virus is unclear. Very few countries report data to the World Organization for Animal Health, which requires Member States to immediately inform them of outbreaks of all erythra and other emerging diseases. "We do need descriptive and analytical epidemiological studies to help us understand the situation in this area," said Mona Dverdal Jansen, a veterinary epidemiologist at the Norwegian Veterinary Research Institute.
this time, WorldFish researchers are working with the Roslin Institute at the University of Edinburgh to develop nile clockers that can fight the virus. An outbreak at WorldFish Pond in Malaysia in 2018 is helping them identify promising genetic variants. In all, there are 1,821 individually labeled salmons in the pond, belonging to a group of 124 siblings. Each group has a different parent. Nearly 40 percent of all fish died; that was enough for the researchers to pick out which group of siblings had the highest survival rates.
, the WorldFish outbreak has allowed researchers to prove that about 50 percent of survival mutations are caused by genes. "This bodes well for future breeding efforts that will increase resistance to viruses," said Ross Houston, a fish geneticist at the Roslin Institute and co-author of the paper. The researchers also found that larger, higher-value fish are just as likely to fight the disease as smaller fish. This finding suggests that farmers will not have to sacrifice yields to increase resistance, which is a problem for them.
, it can take years to put antiviral terfish in ponds around the world. Researchers need a genomic test that allows farmers to quickly identify fish with the ideal gene. They need a reliable and realistic way to infect fish to find out if they are really resistant. Rye cautions that even if farmers succeed in breeding such species, mass production of these fish in hatcheries and their distribution, especially in developing countries, will be a daunting task. "It's not going to change everything overnight," he said.
companies are looking for a different approach: developing a vaccine against the erythra virus. Win Surachetpong, an immunologist at Kasetsart University, says there are some promising signs. For example, his lab found elevated levels of antibodies in virus-exposed clockers. But viable candidates are still a long way off, and even an efficient vaccine may not be cheap enough, especially since thyroid is a relatively low-value fish, often farmed by poor farmers, which is not economically feasible.
benzie said that given these problems and the threat of the virus's continued spread, it has become a "top priority" to develop stronger thyroid species.
relevant paper information:
.