A DOCTORAL research project carried out at the Norwegian School of Veterinary Science (NVH), in collaboration with Norway's Institute of Marine Research, has investigated the use of sterile salmon in aquaculture as a means to prevent escaped farmed salmon from interbreeding with wild salmon.
The study used a method known as triploidy to induce sterility in Atlantic salmon, and the results suggest that in order to successfully integrate triploid salmon into the industry, some modifications must be made to the current protocols to prevent heart and skeletal deformities, an announcement said.
Salmon farming is a major industry in Norway. However, environmental concerns remain over the industry's impact on wild salmon populations. Hundreds of thousands of farmed salmon are reported to escape in Norway each year, and these fish can breed with wild fish, creating hybrids that are less adapted for life in the wild.
The use of sterile fish would prevent this situation. Triploidy, whereby the individual retains the genetic material discarded during fertilization, is the most feasible method to produce commercially available sterile fish, NVH said.
Indeed, triploids are currently used in global shellfish production and salmon production in France and Australia. However, previous work has shown triploids to have more skeletal deformities and lower temperature optima than the diploid salmon currently used in Norwegian aquaculture.
Thomas Fraser's thesis is a study of the potential use of triploid salmon in Norwegian aquaculture in relation to culture practices and heart and skeletal deformities. The main finding of the thesis is that using current culture practices, triploids do have higher levels of skeletal deformities than diploids.
This difference is greater when the salmon are incubated at the higher ranges of temperatures used in the industry. In addition, triploids had a higher prevalence of heart deformities when incubated at the higher temperatures, the announcement reported. Therefore, special consideration with respect to water temperature is required in the production of triploid salmon.
In summary, sterile triploid salmon show potential for use in the Norwegian salmon farming industry, although they are likely to require alterations in culture practices to achieve their greatest potential.