Researchers develop new health test for salmon smolt

The test can provide information that fish farmers will benefit from when transporting smollust salmon from freshwater to sea. The results can help increase the chances of survival for smallpox. Each year, approximately 15 percent of farmed salmon die after being moved from wild freshwater tanks to net pens at sea. Most of these fish die soon after they are transferred – making the test very relevant to the industry.

How do you test for immunity status?

Nofima has developed a diagnostic test that measures the activity of 44 genes that regulate the immune system. A sample is taken from the gills or dorsal fin without damaging the fish.

“A few years ago, we found that the immune system weakens during the unloading process. As a result, we decided to develop a test to measure the immune status of salmon during the heating process,” says Alexey Krasnov, chief scientist at Novima.

To do this, Krasnov and colleagues evaluated multiple genes and selected those that provide the most information about immune status. The scientists collected large amounts of data from various internal experiments at Novima. Krasnov is not aware of any other research body that has a large and well-organized database of gene expression in salmon. The activity of selected genes from different fish culture sites, different groups of fish and different environmental conditions was analyzed. The scientists used this data to develop a database that provides the basis for diagnosing the immune status.

Gene activity reveals the body’s plan

Genes give “commands” for the body’s cells to produce proteins that have a particular function. Genes may increase or decrease activity long before we can see changes in the state of the fish. Scientists measure the activity of carefully selected genes to assess the immune status and health of the salmon.

The scientists determined the normal activity level of each of the 44 genes in healthy fish. If the activity level is too high or too low, this may indicate a poor immune state. This means they can now offer tests for the immune status of smolt salmon.

“We are able to see which fish are in good condition and which are not. In addition, we know which fish look healthy, but are actually not,” says Krasnov.

Industry Representative, Dr. Gordon Ritchie, Director of the Fish Health and Welfare Group at Mowi ASA, co-author of Latest article.

“Successful development of this new technology provides companies with a new tool in the smolt quality assessment box, to check immune efficacy and smolt potency prior to transfer to sea. This immune status diagnostic tool can also be used in future research projects on smolt performance and survival,” Ritchie comments .

Use the new test in other projects

Krasnov also sees the benefits of using the test in other research projects.

“We used the test at the CtrlAQUA Research Center to test whether different methods of producing large smelt in closed recycling facilities affected the immune status before transport to sea occurred. The test showed that the immune status was the same for the different production methods. We also use the test in projects where Nutritionists are investigating whether feed ingredients affect fish health,” says Krasnov.

He is happy to contribute more information to interested parties on how the industry can benefit from this new tool.

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