The Stocking of Hatchery Trout over Wild Populations Revisited

[SlumpBuster]

I've just been doing some searching lately because of classes I'm taking and thought I'd just pass along some of the information that I found to people on the board.

http://dnr.wi.gov/org/caer/ce/news/on/2005/on050222.htm#art2
Good article with an interesting idea for PA. Also shows some points on the limits of hatchery trout.

http://scholar.google.com/scholar?q=author:%22Einum%22+intitle:%22Implications+of+stocking:+ecological+interactions+...%22+&hl=en&rls=com.microsoft:en-US&um=1&oi=scholarr
Very good but long article that shows the effects of stocking hatchery fish onto wild populations.

http://www.pabulletin.com/secure/data/vol27/27-16/594.html
Just the PA criteria for wild trout streams.

Hope some of this info is intersting to some of you. I'll be posting more later and any questions or criticism is welcome (JackM).

P.S. If this gets out of hand Jack you can shut it down. I've been noticing some post lately that weren't really arguments but more like attacks and I just wanted to give some views and discussion on the topic not an argument.

 

[SlumpBuster]

Just some more papers

www.biologicaldiversity.org/swcbd/programs/watersheds/fish-stocking/Eby-et-al-fish-stocking.pdf
Just an overall good paper on the effects of stocking an unnatural fish into a new enviroment.

I think all of these papers show that stocking hatchery fish onto wild stocks of fish are harmful to the wild fish. Hopefully this will help some of you change your minds and will now belive how bad stocking is to wild fish.

 

[JackM]

SlumpBuster wrote:

http://dnr.wi.gov/org/caer/ce/news/on/2005/on050222.htm#art2
Good article with an interesting idea for PA. Also shows some points on the limits of hatchery trout.

"The eggs are hatched at Nevin, and Komassa and Dodge subsequently limit human contact with the fish to keep them wary. They use automatic feeders so the fish do not become reliant on hand feeding or learn how to activate demand feeders. They also use shade covers over the tanks to simulate the cover the fish might find in a stream, and keep the density of fish in the tanks at half that for domestic trout."

This sounds like a very good idea, but as an experiment, I'd say an important control has been neglected. What do we suppose would happen if these rearing techniques were used with hatchery strains of trout? Would the wild strains still out-survive hatchery strains by 2 or 3-1, or we would learn that differences in survival are related more to the conditioning of behavior than to the genetics? I didn't see this addressed in the article.

PS, regarding this:

SlumpBuster wrote:
P.S. If this gets out of hand Jack you can shut it down. I've been noticing some post lately that weren't really arguments but more like attacks and I just wanted to give some views and discussion on the topic not an argument.

An argument is a discussion where all participants do not agree. there is no prohibition on arguments. the only thing we need to do is make sure our attacks, sarcasm, etc. are focused more on the positions taken rather than the individual taking them.

 

[LehighRegular]

What do we suppose would happen if these rearing techniques were used with hatchery strains of trout? Would the wild strains still out-survive hatchery strains by 2 or 3-1, or we would learn that differences in survival are related more to the conditioning of behavior than to the genetics? I didn't see this addressed in the article.

Jack

I think the second link (Long article) that Slump posted discusses genetics. I just skimmed the article, but I think that might address your question. I don't think that exact "study" was performed but the conclusion is that genetics between wild and hatchery strains is a large factor in survival between the two.


That would be an interesting study regardless.

 

[JackM]

I plan to get to the second article later. Too long to read on a break.

 

[RLeeP]

I regularly fish virtually all the streams listed in the WI-DNR news release linked by SlumpBuster. The number of trout in most of them would curl your hair, I kid you not..

All are brown trout fisheries, but as I recall, they are also
trying the same thing in some places they have decided are more suitable for an attempt to establish a trout pop. dominated by or exclusively of brook trout.

Jack's question seems to me to be more of the "What if Superman and God had a fight" variety. Given that as I recall, it is WI's intent to gradually move completely to rearing wild stock and do away with all rearing of conventional domesticated hatchery trout except for the few that are used in the very limited urban ponds/streams program, I don't imagine they care one way or the other whether domestic fish can be induced in the hatchery environment to act more like wild fish through employment of the same regimens. They seem to have chosen a direction to pursue and there has to be a reason for that. My guess is that they believe that genetics is the determining factor in the success of the wild fingerling program and are taking pains not to risk conditioning these attributes out of their wild fish taken for this effort. But I don't know that and I am not a biologist.

All the same, maybe I'll write Dave Vetrano and pose the question to him. It would be interesting to see who he would favor, Superman or God...

SlumpBuster: You might be interested to know that (I'm pretty certain) Iowa-DNR has started doing the same thing with some of their NE Spring Creeks where water quality and whatnot are excellent, but natural spawning habitat is not so good. In terms of topography and geology, NE Iowa is virtually identical to (at least) the southern portion of the Driftless region in WI.

If you search the Iowa-DNR site, I'm sure you find some stuff about this.

An interesting thing about the Iowa program is that they stock adult fish (RT usually) heavily over virtually all their wild trout pops., with the exception of just a couple. I fish North Bear Creek (a stream that due to recent habitat work has had an exponential increase in the wild BT pop.) a couple times each year, usually in October after WI has closed for the season. There are anywhere from 5-15 catchable RT in virtually every pool and lots of singles and doubles in the connecting runs and pocket water. And yet, as noted above, the wild BT pop here is exploding.

Clearly, the damage done by stocking over wild fish, at least in this case, is a very subjective thing..

 

[Chaz]

Something I hadn't considered before that was mentioned in the second article, natural selection would eliminate a certain number of eggs from the gene pool because in some manner they were defective. In a hatchery environment fish culturalists attempt to get as close to 100% of the eggs to hatch as possible. I believe this has huge implications for the population as a whole and also impacts the wild population by introducing fish that would not have survived the egg stage. They also try to create conditions to maximize the fingerling stage, also introducing fish that would have died in a wild population.
I think this speaks volumes, for the argument to not stock hatchery strain fish over wild populations. It also implicates that even if you use eggs from wild stock that you can alter the gene pool by introducing fish that would have otherwise have died during the egg or fingerling stages of development.

 

[JackM]

God and Superman having a fight, OK.

Anyhow, I think people think too simplisticly about breeding and genetics. Some traits can be selectively bred and others cannot in the short timespan we are discussing. A weak fish does not neccessarily produce a weak offspring. A blue eyed Mom may not produce a blue-eyed baby boy, either. This depends also on the father's contribution. Two blue-eyed parents can have all brown-eyed children. It is my suggestion that differences in adaptability of hatchery trout have more to do with conditioning than genetics.

Chaz' point is correct, hatchery breeding may result in a greater amount of inferior hatchery trout available for stocking, because they live in an environment artificially conducive to survival. However, even assuming those fish are more likely to reproduce inferior offspring once contributing to the gene pool in the stream, then those inferior trout will not survive. Yet, some of those hatchery trout, and I dare say even most of them will produce healthy strong offspring that survive as well or better than their wild counterparts.

Unless you are willing to design a study that isolates the effect of breeding from conditioning, I don't think you can draw a conclusion that interbreeding between hatchery trout and wild ones will result in an inferior offspring or pollution of the gene pool. Sorry, but I still haven't read the second article.

 

[JackM]

LehighRegular wrote:

Jack M. wrote:
What do we suppose would happen if these rearing techniques were used with hatchery strains of trout? Would the wild strains still out-survive hatchery strains by 2 or 3-1, or we would learn that differences in survival are related more to the conditioning of behavior than to the genetics? I didn't see this addressed in the article.

Jack

I think the second link (Long article) that Slump posted discusses genetics. I just skimmed the article, but I think that might address your question. I don't think that exact "study" was performed but the conclusion is that genetics between wild and hatchery strains is a large factor in survival between the two.

That would be an interesting study regardless.

I think it was addressed, but I don't read it as saying that genetics is "a large factor:"

"Thus, the success of hatchery produced fish after release appears to be constrained by phenotypic* divergence from their wild conspecifics. This is not surprising given the potential importance of local differences among wild salmonid populations in fitness-related traits and the evidence we have presented concerning the effects of hatchery environments on development and selection."

* phenotype: the observable properties of an organism that are produced by the interaction of the genotype and the environment.