If the transgenic salmon escapes from their pens into the ocean population there are chances that they would compete with the wild salmons for food and space. They may also bring new diseases and changes to the food webs and ecosystem of the ocean.
Explanation:
A transgenic organism or genetically modified organism is the one that undergoes alternation through recombinant DNA technology.
No, I do not think that FDA should approve Aquabounty of growing and selling transgenic salmon since there is higher chance that they may interfere and disturb with the ecosystem and might also bring new diseases.
Selective breeding is when a human or farmer in this case selects two plants or chickens with the best traits in order to get a good yield and quality for the products they are producing. I hope this helps!