Azara Blog: Captive species not fit for survival in the wild

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Date published: 2007/10/05

The BBC says:

Animals bred in captivity to help conservation programmes can quickly become less fit for survival in the wild, research suggests.

US scientists found steelhead trout reared in hatcheries were much less good at reproducing than wild fish.

Writing in the journal Science, they say the use of captive breeding needs careful re-consideration.

For some animals, such as amphibians, captive breeding is being used more and more as wild habitats disappear.

"This study proves with no doubt that wild fish and hatchery fish are not the same, despite their appearances," said Michael Blouin of Oregon State University in Corvallis, US, who oversaw the research.

Steelhead populations in rivers along the US west coast are listed as threatened or endangered by the US Fish and Wildlife Service. Captive breeding and release is one of the measures being used to safeguard numbers of a fish that is much prized by anglers.

The Oregon State team had previously shown that first-generation captive-reared steelhead were just as successful reproductively as their wild-reared relatives, producing just as many young.

In the new study, they compared the success of fish hatched from two captive-bred parents with those possessing one captive-bred and one wild parent.

The results were startling, with the first group about 40% less successful than the second.

"For fish to so quickly lose their ability to reproduce is stunning; it's just remarkable," said Professor Blouin. "If it weren't our own data, I would have difficulty believing the results."

Hatchery programmes for steelhead and other salmonids (species within the salmon family) release more than five billion juvenile fish into Pacific waters each year. So if captive breeding does result in fish markedly less fit and less able to reproduce in the wild, the implications could be significant.

"It's very interesting, and it's not unexpected, it complements what we and other research groups have found for other salmonids," commented Dr Phil McGinnity from the Marine Institute of Ireland.

"The fish are kept in captivity; in domestication, which is basically selection for life in the hatcheries, and in addition relaxation of selection for traits important for life in the wild," he told the BBC News website.

"With wild Atlantic salmon, within two or three months about 90% of the eggs or the fry are dead, so you can imagine that's a large selective effect; whereas in the hatcheries, everybody gets to live, so traits that would quickly be rooted out in the wild are able to survive in the hatcheries. So we're building in that maladaptedness."

As natural habitats disappear, conservationists working on a wide range of species are looking to captive breeding as a bridge to long-term survival.

It is being actively pursued by amphibian specialists, for example.

This is an obvious problem, and everybody who is involved with such schemes must know the risks, even if for political (i.e. fundraising) reasons these problems are swept under the rug. In the same way, botanic gardens do not really preserve wild-type copies of the species they have, because the environment is (normally way) different.

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