Healthier Farmed Salmon

Norwegian researchers have identified the gene that controls a great deal of the fish’s susceptibility to infectious pancreatic necrosis (IPN), a viral disease which has cost Norwegian aquaculture great losses.

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This represents a breakthrough in molecular genetic research and will give a meaningful increase in profits for the aquaculture industry, as a result of fewer losses and better fish welfare. Aqua Gen has already implemented the research results in their practical selective breeding, and has plans to expand the research to include other important viral diseases, such as pancreas disease (PD).

Over time IPN is the infectious disease which has caused most loss in the Norwegian aquaculture industry. Aqua Gen started selective breeding to increase resistance against this disease in 1997. Methods which have been employed so far in this work are based on challenge tests and traditional quantitative genetics. Although a meaningful effect can be documented with this approach, the test methods that are used are quite expensive, and cannot be used in direct testing of breeding candidates.

In 2005 Aqua Gen started a three-year long user-directed innovation project with support from The Norwegian Research Council to identify the genes that are responsible for the salmon’s ability to withstand the viral disease IPN. The project leader is Thomas Moen, AKVAFORSK, and research is carried out chiefly in the CIGENE-milieu at UMB.

Dominant QTL
Regions on the salmon’s chromosomes which are important for the variations in traits which are used in selective breeding are called QTL (Quantitative Trait Loci). In short, the project has identified QTLs which make it possible to identify IPN resistance directly in the fish by means of DNA analysis. The results of the DNA analysis can be used alone in selection, or can be combined with results from challenge tests in order to further increase the accuracy of selection. In the project a QTL has been identified which explains about 70 percent of the genetic variation. The experiment design is so strong that the results have a very high level of statistical significance.

The finding of the dominant QTL and the fact that Aqua Gen’s genetic population shows great variation (heterozygosity), gives good grounds to expect that the new technology will give an important step forward in the work of improving disease resistance and robustness among farmed salmon. Earlier it has been possible to select random fish on the basis of the average performance of families, but now it is also possible to select the best genetic candidates within families with the help of direct DNA analysis.
The first step in the implementation of the research results was made in the autumn of 2007, when breeding fish were selected for Aqua Gen’s robust lineage among other things with the help of the new IPN-marker. It is this selected fish which will produce eggs for the aquaculture industry in the coming generation.

An independent validation of these findings has been made by another research group in Scotland, which has shown the same QTL in the genetic material of Landcatch Natural Selection Ltd. This project started one year before the Norwegian project, and the results have been recently published in a scientific journal. That the same QTL has been found by two independent research groups in two different genetic materials is in itself a strong validation of the findings. In addition, Aqua Gen and AKVAFORSK have taken the research a big step farther by identifying the position of the QTL with much greater accuracy, and by showing that the QTL has the same effect on fry as on the post-smolt stage. The findings give hope that similar procedures can reveal other QTLs which can contribute to combating other important diseases of farmed fish.

Contact persons:
Thomas Moen, AKVAFORSK, telephone 00 47 930 63 956
Arne Storset, Aqua Gen AS, telephone 00 47 970 20 181