Salmon hatcheries have been operating on the West Coast since the late 1800s. Originally hatcheries were used only to increase numbers of wild salmon. Hatcheries can increase the number of fish going to the ocean by artificially spawning and raising fry until they reach the smolt stage. With a better chance of survival at this stage, they are then released into the
ocean.

Large-scale construction of salmon hatcheries began after dams rose in the Columbia River basin. In 1938, Congress passed the Mitchell Act to provide federal money for aggressive construction of hatcheries to replace the thousands of acres of salmon spawning grounds that were blocked or flooded behind dams.

Most hatcheries were built at a time when wild salmon stocks were healthy and genetic diversity was not a concern. Hatchery programs are primarily designed to enhance harvest in commercial, sport and tribal fisheries, or to reduce the impacts of development that destroy or degrade salmon habitat
or block migratory routes. Most propagation programs in the region were designed and funded to produce fish as compensation for habitat impacts. Early hatchery management often involved little more than transporting the biggest, most desirable species of salmon from one river to another. Little
was understood then about the unique genetic makeup of each salmon run, and the "homing" device built into these fish to allow them to find their way back to their native streams.

Hatcheries and the Pacific Northwest are closely intertwined. As the demand for salmon has grown, so has dependence on hatcheries. Hatcheries contribute 70-80 percent of fish in coastal salmon and steelhead fisheries. There are approximately 365 hatchery programs in the region that artificially propagate the six Pacific salmonid species. These programs are operated by the states of Washington, Idaho and Oregon, the U.S. Fish & Wildlife Service, and by Northwest Indian Tribes.

Artificial propagation of hatchery fish presents both potential benefits and risks to the biological status of salmon. Artificial propagation has been shown to be effective in bolstering the numbers of naturally spawning fish in the short term under certain conditions, and in conserving genetic resources and guarding against the catastrophic loss of naturally spawned populations at critically low abundance levels. In recent years, various studies and scientific works have identified some potential adverse effects of artificial propagation, including:

• behavioral differences that result in diminished fitness and survival of hatchery fish relative to naturally spawned fish
• genetic effects resulting from poor broodstock and rearing practices (inbreeding, outbreeding, domestication selection
• incidence of disease
• increased rates of competition with and predation on naturally spawned populations.

In recent years, some hatchery programs have been designed to conserve or recover natural populations of salmon.