The Good, the Bad and the Ugly: California Chinook Salmon and Steelhead Hatcheries and Their Apparent Influence on Wild Stocks

California anadromous salmonids exist at the southern extent of the species range, and over the last half-century have lost access to the majority of historic spawning habitat.  Fall-run Chinook and steelhead hatchery programs were initiated to mitigate for lost habitat, but recently available data suggest hatcheries may be a substantial threat to conservation and recovery of wild stocks.  In 2006, a constant fractional marking (CFM) program was implemented among fall Chinook hatchery programs. Results now available show the proportion of hatchery fish on the spawning grounds (pHOS) and in use as hatchery broodstock (pHOB) in many systems far exceeds what is considered damaging to genetic characteristics and fitness of natural origin stocks.  Steelhead produced in most California hatcheries have been 100% marked since 1998, greatly simplifying estimation of natural origin composition. Similar to fall Chinook, available information suggests wild origin steelhead are being replaced, not just supplemented, by hatchery production. Studies to address the fitness, life history diversity and population viability consequences of hatchery dominance have begun only recently, but findings to date suggest losses in adaptive traits critical to success in California’s unforgiving freshwater, estuarine and marine environments.