Captive breeding 'weakens' fish
By Richard Black
Environment correspondent, BBC News website


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.

Captive loss

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.


This emphasises that you should do everything to stop them disappearing in the first place
Robert Lacy, IUCN
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.

Faults retained

"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.
About one-third of all amphibian species are facing extinction, and the combination of virulent disease, habitat loss, pollution and climatic change means there is often little hope of conserving them in the wild; captive breeding and a re-introduction to the wild at some future point may be the only option.

Robert Lacy from the Chicago Zoological Society chairs the World Conservation Union's (IUCN) Conservation Breeding Specialist Group, and he believes the steelhead finding does raise an important concern.

"A key question is whether the animals can re-adapt to the wild when you re-introduce them," he said.

"If they can, this research suggests you still might need to breed more of them than we would have thought, because the reproduction rate in the earlier generations is going to be lower.

"I think what it also implies is that you would want to make your re-introductions as soon as possible, rather than rearing generation after generation in captivity."

Not all species would be likely to lose their reproductive fitness as quickly as the steelhead. But for those that do, the effectiveness of captive rearing and re-introduction as a survival strategy is now less assured; and relying on a continuing release of captive-reared individuals would prevent re-adaptation.

Said Dr Lacy: "The other thing this emphasises is that you should do everything you can to stop them disappearing in the first place."

"The other thing this emphasizes is that you should do everything you can to stop them disappearing in the first place."

This is about the only thing one needs to take from this....In reality this information on fitness in Captive born fish has been around for quite some time. (1980's and earlier) Nothing is really new about this except for steelhead being the fish named...

I'm sort of involved with some captive rearing efforts, mostly in developing refuge populations of some fish in Nevada. In almost all cases I've seen, captive fish in some way adapt to their captivity, or non-native environment such as ponds, so they are a different fish than what is put in there. Contemporary evolution, the same way non-native fishes become demons in ways we don't fully understand in their introduced habitats. I think some of this is the mentality to mass produce as many fish as possible for direct cost-benefits (looks better to the beancounters to raise 1,000,000 trout instead of 10,000 very fit trout), and it is better to produce fewer but more fit fish in captivity. If you got a pond with fish in it, I'm always arguing to leave stuff like netting off. Sure birds eat some of the fish, but it teaches the other fish in there valuable lessons. Then you got to match what you are raising the fish in with their native habitat, which is next to impossible, and then the genetics, etc...

shawn

Captive breeding 'weakens' fish

Maybe so, but it's better than not breeding fish at all!

Hatcheries that keep broodstock of fish, and use the offspring to creatye future broodstock, are raising weak fish. Hatcheries should look at ways to collect broodstock from the wild, spawn them and release the parents back into the wild. I have seen brook trout in hatcheries with all sorts of problems caused by hatchery raised broodstock, and have seen wild strains that do fantastic when released back into the wild. Most of the hatchery fish have been "conditioned" and are easy targets for predators, including people. I've watched people hang around boat launches with their fishing poles when fish are being stocked. They pretty much slaughter the fish.

Since no one else has mentioned it yet, anyone interested in this captive breeding question should visit the Conservation Fisheries, Inc. web site, http://www.conservationfisheries.org. They have a large facility in Knoxville, TN, for breeding and raising vulnerable species for release under license from various federal and state agencies. The trick is that you have to release young fish to habitat that's able to support them. If you keep and breed fish for generations, with nowhere to go, then you wind up with fish with different physical and genetic attributes; it's really that simple. The fish aren't weakened, merely different.

Within the goodeid hobby we have many, very old strains of documented origin 40-50 years back. None of these fish show any weakness when it comes to reproduction. Obviously they are highly inbreed but that is not a problem, and if you suddenly start pondkeeping them, like we do with some of the in the summer months here in Denmark, they do get all their wild behaviour back within hours. Many fish likes goodeids, cyprinidon etc, change their morphology when kept in captivity, usual gettting much larger, but that is just because their phaenotypes are plastic and adapt to their current enviroment. Maybe a lot of them are already inbreed in the wild comming from rather small habitats? And all the weak genes have already been breed out of the population.

Martin

This is a pretty hot topic - one needs to delimit the term "weaken", and affix some parameters which can actually be measured. Otherwise, it's "I say this!" vs. "I say otherwise!" I'm guessing that not everybody would agree upon what the term means.

This is a pretty hot topic - one needs to delimit the term "weaken", and affix some parameters which can actually be measured. Otherwise, it's "I say this!" vs. "I say otherwise!" I'm guessing that not everybody would agree upon what the term means.

I don't know what everyone else's definition of "weak" is, but my opinion is that hatchery raised fish are in an environment lacking natural parasites and disease. Once exposed to such diseases, their system is unable to cope and they die. They are also conditioned to humans and when the see shadows above the raceways, tend to associate this with "dinner time" and soon become dinner themselves. Not to say that hatcheries are evil, they do a great job propogating species that are otherwise troubled or under immense fishing pressure. Everything depends on how the fish are spawned and raised in the hatchery setting. Just my definition of "weak" for what it's worth.

This is a somewhat tricky definition, even though it appeals to my common sense - you would have to measure mortality in nature vs. mortality in hatchery fish. The thing that complicates matters (to me) is that the survival rate of hatchery fry is surely higher than that of wild fry, and you would need to look at how many fry survive to reproductive age. Now, everybody would probably agree that hatchery fish introduced into the wild at age X have lower survival rates than wild fish of the same age. But this is a small slice of actual mortality as a percentage of hatch. Some of you guys surely have numbers on this?

Conversely, how would the mortality of wild fish which are made captives compare to that of released hatchery fish?
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Aawwww, who cares. Think I'll pop another beer, throw the can in the creek, and make a new madtom house.

This is a somewhat tricky definition, even though it appeals to my common sense - you would have to measure mortality in nature vs. mortality in hatchery fish. The thing that complicates matters (to me) is that the survival rate of hatchery fry is surely higher than that of wild fry, and you would need to look at how many fry survive to reproductive age. Now, everybody would probably agree that hatchery fish introduced into the wild at age X have lower survival rates than wild fish of the same age. But this is a small slice of actual mortality as a percentage of hatch. Some of you guys surely have numbers on this?

Conversely, how would the mortality of wild fish which are made captives compare to that of released hatchery fish?
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Aawwww, who cares. Think I'll pop another beer, throw the can in the creek, and make a new madtom house.

Shoot the can first, then the madtom can have windows! I think there is literature regarding salmonids regarding susceptibility to disease, etc..., but I think this can be minimized by careful management. Plus, even if a few of the fish make it, it is usually for the better when we are talking non-game fish.

I remember I used to be involved with rearing razorback suckers. One day we were releasing them into Lake Mohave, and fairly big ones at that (~250mm), they were swimming off sort of dazed at this new habitat they were put in, and the stripers were swooping in and eating them. I doubt if 1-2% made it. Probably some of that was they were uneducated regarding bad fish, the other part was they weren't used to the new environment. Kinda like when you come out of an airplane in a new airport, and you have that sort of lost feeling. If a pride of lions were there, we'd be easy prey.

Shawn