Sterile salmon

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Updated documentation, per September 2013

 

AquaGen first introduced eggs for the production of sterile salmon in the season 2012/13. The main reason in Norway for producing these eggs is that sterility eliminates some of the possible negative impacts that escaped farmed salmon could have on wild salmon. Sterile salmon can also reduce other problems such as undesirable early maturation prior to harvest weight. The only available method for producing sterile eggs today is triploidization. Just after fertilization eggs are treated in a pressure chamber, resulting in the fish having three sets of chromosomes instead of two (diploid).

Egg production

Figure 1. Egg containers are taken horizontally into the pressure chamber (to the left) for triploidising. With this automatic equipment eggs that are at a very vulnerable stage are gently handled.

Figure 1. Egg containers are taken horizontally into the pressure chamber (to the left) for triploidising. With this automatic equipment eggs that are at a very vulnerable stage are gently handled.

AquaGen has installed newly developed equipment that can process large volumes, and that gives eggs a gentle and uniform treatment (Figure 1). The latter is essential for good survival during early development. For the first production in the project mentioned below, the average mortality between egg delivery and first feeding was 3.2% and 2.4%, respectively for triploids and diploids. The new pressure chamber has been verified to produce 100% triploid eggs (Figure 2).

Production of triploid salmon

AquaGen is currently participating in a project with five fish farming companies, to test the large-scale commercial production of triploid salmon. The first fish involved in this project were first-fed in 2013. This project will provide information to complement existing research based knowledge that has been built up over the last 20 years.

Growth: Triploid salmon grows at least as well as diploids in freshwater, and up until body weight of 2-3 kg in seawater. From then on growth rate reduces, and in the final phase until harvest weight of 5-6 kg, then approximately 10% less weight should be expected compared to diploid. Experiments with long term exposure at elevated temperatures (19 °C) and low oxygen content (< 70% saturation) have shown that triploids are more sensitive to these environmental factors than diploids.

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Figure 2. Testing of yolksac fry that were triploidised using the new pressure chamber. Test method used was flow cytometry, showing as expected that the average cell content of DNA is exactly 1.5 times higher in triploids than in diploids.

Animal welfare: Triploid salmon have a higher incidence of skeletal deformities, but this will reduce to the same level as diploids by increasing the phosphorous content of feed in freshwater and the first three months of the seawater phase (> 0.9% available phosphorus). A greater incidence of cataracts can be reduced if the food contains sufficient histidine (> 1.8%).

Products that can be sterile:

  • AquaGen® Atlantic QTL-innOva® IPN
  • AquaGen® Atlantic QTL-innOva® IPN/RED
  • AquaGen® Atlantic QTL-innOva® IPN/PD
  • AquaGen® Atlantic QTL-innOva® IPN/PD/RED

Benefits with sterile salmon:

  • Escaped sterile salmon cannot reproduce and affect the genetics of wild salmon stocks
  • Reduced quality problems with early maturation
  • Increased flexibility in relation to harvest time