I bet you didn't know that 1/3 of Alaska salmon is hatchery raised?  So how is 1/3 a "majority?"  Hatchery fish have to work for a living and feed off forage fish, not pellets packed with steroids and antibiotics like farmed raised.  Also, hatchery fish are "terminal harvest."  They swim back to the hatchery when they are ready to spawn and do not interfere with wild stock reproduction.
http://www.adfg.alaska.gov/index.cfm?adfg=pressreleases.pr03302016