This article from Comstock’s Magazine says hatchery salmon are genetically inferior, the argument environmentalists who oppose dams have been using for decades; but the best response I have heard to that came from Congressman Tom McClintock who says that the difference between hatchery-born salmon and wild-born salmon can be compared to human children born in the hospital to children born outside of it.
An excerpt from the Comstock’s article.
Every spring and summer, Chinook salmon gather in vast schools along the central coast of California, fattening up on krill and small fish before their autumn spawning migration into the Central Valley. Fishermen in commercial boats, private skiffs and kayaks take to the water, and most summers, the fleet catches several hundred thousand Chinook weighing somewhere between five and 30 pounds. Many more are caught by fishermen in the Sacramento River and its tributaries.
California’s bounty of salmon, however, does not reflect a thriving fish population. Rather, many, if not most, of California’s salmon are born in five Central Valley hatcheries and released into the wild as juveniles. Without these facilities — including one just below Folsom Lake — there would be almost no salmon at all in some years. That’s because upriver dams and powerful irrigation pumps in the Sacramento-San Joaquin Delta have made the valley’s rivers nearly incapable of supporting natural spawning runs. And while thousands of adult fish lay and fertilize eggs in the gravel beds of the Sacramento River and its tributaries each year, most offspring die before reaching the ocean.
But the hatchery life-support system the salmon fishery depends on is fraught with problems and is causing unintended side effects that may be doing more harm than good. While the facilities have masked a precipitous decline in naturally spawning salmon populations, hatcheries are also doing something else: By removing or altering many of the natural selection mechanisms by which Chinook salmon evolved to thrive in California’s arid climate, they are creating a genetically inferior fish. When spawning time comes, many hatchery-born salmon pair up with salmon of increasingly threatened natural lineage and, in doing so, pass on their genetic deficiencies.
Retrieved August 11, 2015 from http://www.comstocksmag.com/article/survival-fishes?utm