As far as I know, Salmo domesticus, is like a chicken. Paul Greenberg described how they first created the frankenfish in Four Fish, and frankenfish is the right word for it. They took a bunch of different strains of Atlantic Salmon and bred them together, selective breeding, and created a fish that grows fast, doesn’t eat as much, and doesn’t mind living life in a pen. Amazingly, the fish seem to be able to adapt to life like a normal salmon when they break free and survive. In Four Fish, Greenberg does state that these frankenfish manage to breed in rivers and carry on with their steelhead-esque life, slowly bringing salmon runs back to the East Coast of Canada. Although that is a good thing in my mind, and I also like the fact that they manage to really take strain off of the wild salmon left, I feel that farming them in the Pacific Ocean and down in the Southern Hemisphere can be incredibly harmful due to the same reason they are a good thing in the Atlantic. I have heard reports of pens breaking open in British Columbia and the salmon running up rivers on the West Cost, making them an invasive species.