Why are some hatchery salmon being killed?
A number of studies, involving at least five species of salmon, have found genetic differences between hatchery fish and wild fish that make the hatchery fish less successful for reproducing or rearing in natural streams. No studies have shown otherwise. Apparently, genetic adaptation for success in hatchery programs comes with the cost of reduced success for natural (wild) production. This genetic difference is a problem where hatchery fish interbreed with wild fish in natural spawning areas because interbreeding should reduce the health (adaptedness, production, and resilience) of the wild population. Many people who care about the health of salmon populations do not understand how society can expect loggers, farmers, miners, industrialists, and others to avoid harming wild salmon populations while hatchery programs are allowed to harm wild salmon. Safeguards, such as killing surplus hatchery salmon rather than allowing them to swamp an already depressed wild population, are being implemented to avoid or reduce inadvertent harm to wild populations from hatchery programs.