We may not be able to count on zoos and captive breeding to save wildlife

July 2, 3:55 PMWildlife Conservation ExaminerCathy Taibbi

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Chinook Salmon. Photo Oregon State Unviversity

A recent news release has sobering implications for our options in restoring damaged ecosystems.

The report, released by Oregon State University, found that introducing hatchery fish into wild waterways may actually hurt efforts to sustain runs of wild salmon.

This is very alarming, considering the ‘safety net’ humans thought we had in preserving a multitude of threatened and endangered species through captive-propagation.

Zoos, managed sanctuaries, Species Survival Plans, private breeding facilities and hobby breeders (including, by the way, this author) have all believed that they were creating a network of “Noah’s Arks” with which to re-populate decimated ecosystems, or to restore species that are now extinct in the wild (existing only in captivity).

Until now, few questioned the logic or viability of such efforts, as the work of thousands of Zoos, parks and small private hobbyists (raising reptiles, parrots, fish, exotic cats, rhinos and more), can attest. Most of these individuals and groups exist, not for profit, but to perform a dual task: to educate, and to preserve genetic- and bio-diversity.

Their efforts, at least as currently performed, may be in vain.

According to the news release, “Steelhead trout that are originally bred in hatcheries are so genetically impaired that, even if they survive and reproduce in the wild, their offspring will also be significantly less successful at reproducing.

“The poor reproductive fitness – the ability to survive and reproduce – of the wild-born offspring of hatchery fish means that adding hatchery fish to wild populations may ultimately be hurting efforts to sustain those wild runs.”

Even if one of the parents of a captive-hatched fish is from wild stock, the degraded quality of the offspring, a generation later, is still evident in those survivors, despite subsequently being selected through wild pressures.

The report goes on to say that the effect of hatcheries on reproductive fitness in succeeding generations had been predicted in theory, but until now had never been demonstrated in actual field experiments.

"If anyone ever had any doubts about the genetic differences between hatchery and wild fish, the data are now pretty clear," said Michael Blouin, an OSU professor of zoology. "The effect is so strong that it carries over into the first wild-born generation. Even if fish are born in the wild and survive to reproduce, those adults that had hatchery parents still produce substantially fewer surviving offspring than those with wild parents. That's pretty remarkable."

According to the news release, an earlier report, published in 2007 in the journal Science, had already shown that hatchery fish that migrate to the ocean and return to spawn leave far fewer offspring than their wild relatives. The newest findings suggest the problem does not end there, but carries over into their wild-born descendants.

The implication, Blouin said, is that hatchery salmonids – many of which do survive to reproduce in the wild– could be gradually reducing the fitness of the wild populations with which they interbreed. Those hatchery fish provide one more hurdle to overcome in the goal of sustaining wild runs, along with problems caused by dams, loss or degradation of habitat, pollution, over-fishing and other causes.

Aside from weakening the wild gene pool, the release of captive-bred fish also raises the risk of introducing diseases and increasing competition for limited resources, the report noted.

This research, which was just published in Biology Letters, was supported by grants from the Bonneville Power Administration and the Oregon Department of Fish and Wildlife. It was based on years of genetic analysis of thousands of steelhead trout in Oregon's Hood River, in field work dating back to 1991. Scientists have been able to genetically "fingerprint" three generations of returning fish to determine who their parents were, and whether or not they were wild or hatchery fish.

The underlying problem, experts say, is Darwinian natural selection.

Fish that do well in the safe, quiet world of the hatcheries are selected to be different than those that do well in a much more hostile and predatory real-world environment. Using wild fish as brood stock each year should lessen the problem, but it was just that type of hatchery fish that were used in the Hood River study. This demonstrates that even a single generation of hatchery culture can still have strong effects.

Although this study was done with steelhead trout, it would be reasonable to extrapolate its results to other salmonids, researchers said. It's less clear what the findings mean to the many other species that are now being bred in captivity in efforts to help wild populations recover, Blouin said, but it's possible that similar effects could be found.

As stated at the beginning of this article, captive breeding is now a cornerstone of recovery efforts by conservation programs for many threatened or endangered species. “Thousands of species may require captive breeding to prevent their extinction in the next 200 years – which makes it particularly important to find out if such programs will ultimately work. This study raises doubts.”

"The message should be clear," the researchers wrote in their report's conclusion. "Captive breeding for reintroduction or supplementation can have a serious, long-term downside in some taxa, and so should not be considered as a panacea for the recovery of all endangered populations."

This should be a wake up call to all of us that the well-being of our wild, natural world, and every habitat and species in it, should be considered precious and irreplaceable. We, as humans, cannot do a better job of managing nature than nature does on its own. What we need to do is stop our relentless expansion and exploitation, and allow nature to come back.

Only a recovered Earth is a sustainable Earth.

About the OSU College of Science: As one of the largest academic units at OSU, the College of Science has 14 departments and programs, 13 pre-professional programs, and provides the basic science courses essential to the education of every OSU student. Its faculty are international leaders in scientific research.

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