Re: NANFA-L-- Review of Suckers in North America

Subject: Re: NANFA-L-- Review of Suckers in North America
dlmcneely at
Date: Tue Oct 12 2004 - 12:36:00 CDT

Not at all. What I'm saying is that the fish produced in hatcheries come from far fewer parents than the fish that live in the wild. Since there are fewer parents, these fish vary less genetically than do fish in the wild. Plus, the fish kept in hatcheries are the fish that did well in hatcheries over a series of generations. They've been naturally selected by the conditions of hatchery life, and they are well suited to those conditions. To release their progeny into the wild is like releasing cattle from a dairy herd or horses from a thoroughbred outfit to fend for themselves on the prairie. Some might make it, but not many, and their genetic heritage is against them.

This in fact is one of the problems with hatchery release of salmon to replenish the populations that have been depleted. Data show that you cannot replenish salmon stocks with hatchery fish, even where habitat remains excellent, but that if enough wild salmon are allowed access to the spawning grounds, populations remain healthy. Even if the wild replenishment seems unlikely because of homing behavior of adult salmon, strays will take care of the matter.

Couple the monoculture, domesticated herd of fish genetic problem with the steep learning curve already mentioned, and hatchery fish fare poorly when released. That was ok by fishery managers who simply wanted to dump some catchable sized trout out for people to try to catch. But it doesn't work for stock replenishment.

Where effort is made to produce animals for reintroduction in as nearly wild conditions as possible, as at the CFI labs and a lot of captive reared programs for mammals, that seems to be working better. Plus, darters, madtoms, shiners reared for reintroduction are usually only one or two generations removed from the wild, unlike the experience with salmonids. In Washington state, genetic analysis of returning fish shows that very few hatchery fish actually return, compared to the proportion of wild fish.

Lets look at your analogy a little further. Of course, just because you cut off a rat's tail, doesn't mean that it's offsping are any more likely to be tailless than any other rat's offspring. But suppose you have a laboratory colony of rats, and at random times, you catch a few. If the rat is easily caught, you move to the next step. You hold it, place it on a block. If it doesn't scratch and bite, you cut off its tail, and place it in a breeding colony. If it does scratch and bite, it is kept away from other rats, and not allowed to breed. Rats in the original lab population also are not allowed to breed. Only the rats that were easy to catch, and that were docile under handling, and had their tails docked, are allowed to breed. You won't breed tailless rats, but you will breed docile rats.

That's what we've done with domestic animals, fish included. And they don't fit the wild conditions that produced their ancestors.

This probably applies less to modern captive breeding programs for threatened and endangered animals than it does for typical hatchery animals.

David L. McNeely, Ph.D., Professor of Biology
Langston University; P.O. Box 1500
Langston, OK 73050; email: dlmcneely at
telephone: (405) 466-6025; fax: 405) 466-3307
home page

"Where are we going?" "I don't know, are we there yet?"

----- Original Message -----
From: Moontanman at
Date: Tuesday, October 12, 2004 11:39 am
Subject: Re: NANFA-L-- Review of Suckers in North America

> In a message dated 10/12/04 12:08:46 PM Eastern Daylight Time,
> dlmcneely at writes:
> > Natural selection for success in hatcheries? Less genotypic
> variability?
> > Hatchery fish are the progeny of a restricted set of parents
> compared to wild
> > fish.
> >
> >
> So what you are saying is that if you catch two fish and breed
> them their
> progeny will be less able to survive than the young of two fish
> who have stayed
> in the wild? Isn't that a little bit like saying that if you raise
> rats and cut
> off their tails each time eventually the rats will have shorter tails?
> moon

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: Fri Dec 31 2004 - 11:27:43 CST