# Science article: Captive breeding = rapid fitness decline



## dneafse (Nov 1, 2006)

An article published October 5, 2007 in Science should raise questions about the potential conservation merits of frog-keeping, or any captive breeding programs for species that are merely in decline rather than critically endangered. The article only tracks fitness over a couple of generations in steelhead trout, and so the fitness consequences the authors report presumably derive only from artificial/weakened selection imposed by captivity. Inbreeding and novel mutations could be expected to worsen the fitness decline over longer time periods. 

At the very least, this article suggests that regular infusions of new imports would be required to sustain the genetic viability of captive lineages of locality-specific morphs, if one hopes to ever use captive populations to restore declining wild populations.

http://www.sciencemag.org/cgi/content/a ... 8/5847/100

Genetic Effects of Captive Breeding Cause a Rapid, Cumulative Fitness Decline in the Wild
Hitoshi Araki,* Becky Cooper, Michael S. Blouin

Captive breeding is used to supplement populations of many species that are declining in the wild. The suitability of and long-term species survival from such programs remain largely untested, however. We measured lifetime reproductive success of the first two generations of steelhead trout that were reared in captivity and bred in the wild after they were released. By reconstructing a three-generation pedigree with microsatellite markers, we show that genetic effects of domestication reduce subsequent reproductive capabilities by ~40% per captive-reared generation when fish are moved to natural environments. These results suggest that even a few generations of domestication may have negative effects on natural reproduction in the wild and that the repeated use of captive-reared parents to supplement wild populations should be carefully reconsidered.

Department of Zoology, 3029 Cordley Hall, Oregon State University Corvallis, OR 97331, USA.


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## Ed (Sep 19, 2004)

There are some problems when trying to use this article as applied to dart frogs and other animals... I have to see if I saved my notes on a discussion on this paper. If I can find them then I'll have some coherent comments otherwise I'll come back to it with what I can remember. 

Ed


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## bbrock (May 20, 2004)

This has been making it rounds. Here is a link to an article on the subject:

http://news.bbc.co.uk/2/hi/science/nature/7026997.stm

This was discussed in some detail on frognet but making inferences from this paper and amphibian captive breeding programs is dangerous and i think it is actually a bit irresponsible that they made that very inference in the above article.

The differences between fish hatchery captive breeding and what is being proposed for amphibians are vast. Hatcheries use very sterile, mechanized, and industrial propagation methods which produces a very strong selection pressure on the billions of fish eggs and fry processed each year. More importantly, hatchery fish are used a a chronic supplementation of wild populations and it has always been a bad idea. Originally, hatcheries were designed simply to provide more catchable fish for anglers and commercial fishermen but in recent decades, they have been used as a replacement for maintaining high quality spawning habitat. That's simply not good natural resource management.

In contrast, nobody is suggesting that amphibians should be chronically reared in captivity as a substitute for them being able to reproduce in the wild. Rather, the plan is to do short term reintroductions to restore wild populations that have already been lost. That there would be higher than normal mortality, and lower than normal reproduction, in these first releases is pretty much expected. But you only have to get enough of them to reproduce in the wild to begin to rebuild a stable population that is re-adapted to wild conditions.

Comparing fish hatcheries with more "typical" captive breeding programs is apples and oranges. That said, I would really like to get my hands on the full text of the original Science pub. It's impossible to tease out the details of the methods and results from abstracts and press articles.


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## bbrock (May 20, 2004)

Thanks to Dan, I've now had a chance to read the full paper on the effects of captive breeding on hatchery fish. Not an easy read. But my earlier criticisms about applying this to frogs has not changed. Even the authors suggest the most likely reason for the results they report is that hatcheries impose very strong selection for domestication and relax selection for wild traits. Thus, although they demonstrate these differences are genetic, they also suggest that the genetic differences are created by the vastly different environments of hatcheries compared with the wild.

There is a lesson here for frog keepers though. When we pull eggs from the parents and raise tadpoles outselves, we are managing very similar to a fish hatchery. This is why many people have argued for allowing frogs to complete their natural lifecycles without intervention to prevent strong selection for domestication. You can't eliminate all selection pressures, but fish hatcheries are a pretty severe departure from wild conditions and we should do our part to avoid these problems in captive amphibians.

BTW, the paper never mentions captive breeding for frogs. That comparison was made completely by the journalist reporting on the paper. Which was my suspicion. But it really is an unfair comparison.


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