Saturday, November 28, 2009



As wild salmon and steelhead populations decline toward extinction in the Northwest, and many have already gone extinct, recovery has been based on the assumption that wild salmonids can be rebuilt using hatchery technology.

Since the first wild salmon and steelhead populations were listed in 1991 in the Columbia River basin more than $8 billion dollars have been spent on salmon recovery. If money were enough wild salmon would have increased rather than continued to decline. The federal response to the court has been that “trending toward recovery” is good enough to justify this investment of public funds.

During the past eighteen years of salmon recovery efforts, attention has been on hatchery supplementation of wild salmonid populations rather than on developing a recovery program for wild populations. A program for wild salmon and steelhead recovery would adopt river specific conservation requirements. But this has not been done. Consequently, the vast amount of public funding for salmon recovery has not been effectively applied. It is not how much money has been spent, but how it is spent.

There are now two opposing recommendations on the use of hatcheries to rebuild wild salmonid populations. Congress recently funded a hatchery review by the Hatchery Scientific Review Group (HSRG) that has recommended many important hatchery modifications to improve their operations and reduce their impact on wild salmon and steelhead. However, the HSRG has recommended an untested premise. By including wild fish in the hatchery brood stock and limiting the number of hatchery fish that spawn naturally with wild fish this so-called integrated hatchery concept can be used not only to protect the wild population, but increase its size.

The other recommendation comes from a separate research project that evaluated the effect of hatchery fish, derived from native, wild brood stock, on wild fish when they spawn together naturally in streams. This study concludes that the hatchery fish that spawn naturally with wild fish are a drag on the productivity of the wild population, reducing their fitness and reproductive success. Wild fish the hatchery program was intended to help are exposed to greater risk. This study also shows that this effect spans several generations, that is, when progeny from wild born hatchery fish return and spawn, their progeny are less productive than wild fish, producing fewer surviving adult progeny. And when these fish spawn naturally with wild fish the reproductive fitness of progeny is reduced. In addition, this detrimental effect is genetic and is not erased by natural selection in the stream and ocean.

The findings of this research and the recommendations of the HSRG are in conflict. The HSRG says that some naturally spawning hatchery fish is okay, but the research says that naturally spawning hatchery fish degrade the fitness and reproductive success of wild fish and that this impact increases with each generation.

The following are some quotes from a 2009 scientific paper that describe this hatchery effect on wild fish:

“…relative reproduction fitness was only 37% in wild born fish from two captive-bred parents and 87 per cent in those from one captive-bred and one wild parent (relative to those from two wild parents. Our results suggest a significant carry-over effect of captive breeding, which has negative influence on the size of the wild population in the generation after supplementation. In this population, the population fitness could have been 8 per cent higher if there was no carry-over effect during the study period.”

“…genetically-based loss of fitness in the wild has been well documented (Reisenbichler and McIntyre 1977, Reisenbichler and Ruin 1999, Araki et al. 2007, 2008). Thus, captive-bred organisms could potentially drag down the fitness of the wild populations they are meant to support, even while temporarily boosting their numbers.”

“We examined the reproductive fitness of captive-bred fish in the wild using the same molecular technique, in the same population (Hood River, Oregon). The results suggest that first-generation hatchery fish were reproductively less fit than wild fish, and that second generation hatchery fish were even less fit than first generation fish.”

“The estimated reduction in fitness of captive-bred fish was up to 40 per cent per generation. Now we ask whether their wild-born offspring, which successfully survived a full generation of selection in the wild, can have as many adult offspring as wild fish that have not been influence by captive-breeding.”

“Now we ask whether their wild-born offspring, which successfully survived a full generation of selection in the wild, can have as many adult offspring as wild fish that have not been influence by captive breeding. This comparison provides a unique opportunity to estimate the change in wild population size owing to any carry-over effect of captive breeding. “

Over all three years there is a clear pattern of decline in reproductive fitness in order of W (w x w) > W (derived from captive x wild origin parents ) > W (derived from captive x captive origin parents).

“The fitness difference persisted despite a complete life cycle of natural rearing, during which time natural selection had the opportunity to eliminate less fit individuals from the population…”

“We estimated that this carry-over effect reduced population fitness by 8 per cent relative to a purely wild population of the same size.”

“Given that the genetic effect of captive breeding was not erased by a full generation in the wild, supplementation programmes could have a cumulative impact on wild populations.”

“The message should be clear: captive breeding for reintroduction or supplementation can have a serious, long-term downside in some taxa, and should not be considered as a panacea for the recovery of all endangered populations.”

Until this research was done, it was assumed that by using native brood stock, the hatchery and the wild fish were the same, that they had the same reproductive fitness. The wild fish would be enhanced and hatchery fish survival increased. On that basis the fish management agencies initiated numerous native brood stock hatchery programs. Now that this research points out the fallacy of this assumption, will the agencies correct the problem?

This study also points out a fallacy in the HSRG recommendation that would allow a proportion of the naturally spawning population to be of hatchery-origin fish. If this advice is followed the hatchery fish (even those derived from wild parents) would negatively impact the reproductive fitness of the wild population they interbreed with.

It is evident that hatchery technology cannot be used to recover wild salmonid populations. However, this research implies, but does not profess, that hatchery fish survival can be improved by incorporating wild fish into the hatchery broodstock, but it is necessary to have access to healthy wild populations. This higher survival could increase contribution to the fisheries and reduce the cost of putting a fish into the catch. However, in doing so, the wild fish are exposed to higher risk.

This illustrates a fundamental conflict ingrained in the fish management agencies between conservation and utilization. If this conflict did not exist, the fish agencies would not have assumed wild salmonids could be recovered with hatchery fish with out proof and they would not have moved ahead with native brood stock hatcheries on the assumption there was no risk to the affected wild populations.


Araki, Hitoshi, Becky Cooper and Michael S. Blouin. 2009. Carry-over effect of captive breeding reduces reproductive fitness of wild-born descendants in the wild. Conservation Biology. Biology Letters. Rsbl. 2009.0315.

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