Posted by Robert Depue: Farm raised trout and salmon can now be raised so that they are sterile. How this is done is by making them have three chromosomes which makes them unable to interbreed with wild fish or to breed at all. This process is done by taking an engineered fish that has four sets of chromosomes and crossing it with a regular fish with two chromosomes. The fish with three sets of chromosomes, because it does not have to waste energy on reproduction, can spend that energy on growth. Because these fish can’t breed, they would not be an invasive species of fish if they got out of their farms because they would die off.