Alaskan salmon swim around in the wild, eating what nature intended them to eat. Therefore, their nutritional profile is more complete, with micronutrients, fats, minerals, vitamins, and antioxidants (which gives salmon its pink, or in the case of sockeye, red-colored, flesh.)
Farmed salmon, on the other hand, are fed an artificial diet consisting of grain products like corn and soy (most of which is genetically modified), along with chicken meal, artificial coloring, and synthetic antioxidants, which is not approved for human consumption, but is permitted to be used in fish feed.
Mother Nature never intended fish to eat these things, and consequently farmed salmon taste different than wild-caught, and much of it has to do with the altered fat ratio, which is dramatically different. Farmed salmon contain far more omega-6, courtesy of their grain-based diet.
Wild salmon typically has 600 to 1,000 percent more omega-3s compared to omega-6s. This is important, because if you’re trying to improve your omega-3 to omega-6 balance, you simply will not accomplish it with farmed salmon.