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Can We Trust Hatcheries for Salmon Recovery?
When a juvenile salmon pokes its odd looking head out of the gravel for the first time, it faces an extraordinarily harsh world. The chances of survival are pretty slim, probably much less than one percent on most streams. The dangers are many; just figuring out what food is and where it is available has to be challenging for a fish less than an inch long, especially when there are a whole host of predators that target one inch fish. Fortunately, instincts kick in right away and the salmon buddy-up in groups to scour the downstream flow of food and dodge predator fish and birds. Safety in numbers! The longer a fish spends in habitats that support good food sources and offer cover from predators, the better their chance of survival in the hostile marine environment.
In the racks of trays at any one of the hatcheries that are providing the mitigation for the loss of so much habitat behind dams, the eyed salmon’s first peak of the world is a nursery with thousands of like eyed clones. Next stop is the feeding pen where they will spend months being spoon fed pelletized food, much like an in industrial chicken farm. The young salmon grow quickly with incredible survival rates, and this would seem like an excellent way to make up for the loss of habitat. However, more and more research is suggesting that we may be harming wild fish more by introducing so many hatchery fish.
NOAA Fisheries released a report from the Northwest Fisheries Science Center in February of this year identifying many of the risks to wild salmon populations. The following excerpts demonstrate how hatcheries can release genetically inferior salmon while at the same time competing with wild fish for food and space. The full report can be found at: www.nwfsc.noaa.gov/resources/salmonhatchery/risks.cfm.
Human intervention in the rearing of wild animals has the potential to cause genetic change. These genetic changes impact salmon diversity and the health of salmon populations.
Inbreeding can occur when the population for a hatchery comes from a small percentage of the total wild and/ or hatchery fish stock, reducing the genetic diversity within a population.
Inbreeding can affect the survival, growth, and reproduction of salmon. Intentional or artificial selection for a desired trait is not common practice today, although some hatchery programs intentionally select for larger fish. This selection changes the genetic makeup of the hatchery stock, moving it further away from naturally reproducing salmon stocks.
Selection resulting from nonrandom sampling of broodstock can be a problem for hatchery fish. If, for example, only early-returning adults are used as broodstock, instead of adults that are representative of the population as a whole, there will be genetic selection for salmon that return early.
Hatcheries rear fish in vessels that are open and have lower and more constant water flow than that in natural streams and rivers. As a result unintentional or natural selection often occurs in the hatchery environment. Fish are held at higher densities than those that occur in nature which can favor fish that best survive in hatchery, not natural environments.
Artificial mating disrupts natural patterns of sexual selection. In hatcheries, humans select the adult males and females to mate, not the salmon. Humans have no way of knowing which fish would make the best natural breeders.
Ecological risks of artificial propagation on wild populations include competition between wild and hatchery fish. It is most likely to occur if the fish are of the same species and they share the same habitat and diet.
Hatchery environments are different than stream environments. Hatcheries typically rear fish in vessels that produce sterile environments where there is no underwater structure, little or no overhead cover, and a predictable food supply. Consequently, hatchery fish tend to have different foraging, social, and predator-avoidance behavior.
Large-scale releases of hatchery fish have supported commercial, tribal, and sport fishing practices for many years. However, large-scale releases of hatchery fish in a mixed-population fishery create a risk of overfishing for wild populations. For example, if fishers are allowed to catch half of the more abundant, hatchery stocks, half of the wild stocks will also be harvested if they occur at the same time and place as the hatchery fish. Because hatchery populations have high survival in the hatcheries, they can generally support higher harvest rates. Wild stocks with typically much smaller populations could be harmed by such high harvest rates. Selective harvest of hatchery fish through catch and release programs may help.
The effects of disease on hatchery fish and their interaction with wild fish are not well understood. Hatcheries can have disease outbreaks. Once released, these fish can transmit disease to wild fish.
The Hatchery Science Review Board for the Report to Congress for the Columbia River Hatchery Reform has provided some excellent thoughts on where we are today. “Hatchery fish cannot replace lost habitat or the natural populations that rely on that habitat. Therefore, hatchery programs must be viewed not as surrogates or replacements for lost habitat, but as tools that can be managed as part of a coordinated strategy to meet watershed or regional resource goals, in concert with actions affecting habitat, harvest rates, water allocation, and other important components of the human environment."
The American Fisheries Society, Cal Neva Chapter, recently held a forum on Hatchery Reform. It was agreed that “hatcheries in California are now recognized as a significant and persistent threat to the viability of natural origin Chinook salmon populations and fisheries.” (Lindley et al. 2009) We will likely never successfully recover our salmonids with the current level of dependence on hatchery production. It is time for change.