Hatcheries, while widely used to supplement harvest, cannot adequately replace wild salmon and steelhead
Since the middle of the 20th century, hatcheries have been widely used to supplement sport and commercial fisheries, mitigate for habitat lost to dams and to replace populations of wild salmon declining from overharvest and habitat degradation. Increasingly however, science tells us that hatcheries cannot adequately replace wild salmon and steelhead, and that large scale hatchery production is incompatible with healthy wild populations.
Hatchery fish experience a fundamentally different environment than their wild counterparts and research has repeatedly shown that even a single generation of hatchery domestication can reduce the reproductive success – how many adult offspring a fish produces – by up to 70%. In hatchery stocks that have been domesticated for several generations, reproductive success is almost zero. In the wild natural selection acts strongly throughout the life of a fish, allowing only the fittest individuals to survive, breed and pass their genes on to the next generation. Hatcheries relax or alter these selective pressures in almost every phase of a salmon’s life. From juvenile rearing behaviors to redd site selection and egg size the hatchery environment produces fish that are dramatically different than their wild counterparts. When these hatchery fish spawn with wild, the survival of the resulting offspring is significantly diminished, reducing the productivity and abundance of the wild population.
While much has been made of the importance of using wild broodstock programs to protect “native genetics”, they are not a panacea. Genetic differences between hatchery and wild populations are only a small part of the equation, and fitness differences between hatchery and wild stocks can occur without measurable genetic change.
The ecological impacts of hatcheries are also increasingly being highlighted as cause for concern for wild populations. Production hatcheries release several billion hatchery salmon and steelhead each year. These fish, often larger than their wild counterparts compete for finite resources with wild fish, prey upon wild juveniles, spread disease, and attract predators. Furthermore, many of these fish will remain in freshwater and wild fish in most systems are subject to competition and predation from residualized hatchery fish.
In many cases fisheries targeting hatchery fish also catch wild fish. However high exploitation rates on hatchery populations can depress or even extirpate sympatric wild populations. This was the case in the 1970’s when fisheries targeting coho produced by Mitchell Act hatcheries in the Lower Columbia drove upper Columbia and Snake River coho to extinction through overfishing.
If we hope to recover wild salmon and steelhead in the Pacific Northwest hatchery reform must be a part of the equation. This means dramatically reducing the number of hatchery fish spawning in the wild, and eliminating hatchery programs altogether in watersheds where habitat conditions can support robust populations of wild fish. Wild salmon and steelhead have the capacity to be tremendously productive when left to their own devices in a healthy watershed free from hatchery influence; it’s up to us a society to have the courage to let them try.