Pond Boss Forums INTRO Questions & Observations Link says Captive salmon offspring decline

short laymen summary that may be of interest to community

http://www.nytimes.com/2007/10/09/science/09obbree.html?ref=science

Without digging deeply into the study, it sounds like junk science to me.

The main question that comes to mind is, how do they count the wild-hatched fry? At hatching, or after nature has already sorted them out?

Captive egg hatching rates is probably very high. Many marginal eggs probably hatch, and marginal fry survive to releasing size.

Wild egg hatching rates are probably much lower, and by the time the fry are the size to be included in a study, only the vigorous ones have survived. So the deck is stacked.

I don't see a downside to hatcheries. Even though the survival *rate* may possibly be lower, the number of survivors are probably equal.

Look at the source NYT. This is IMHO a great example of how science is mis-used for a political purpose. The whacko's want to stop the hatchery breeding of salmon etc. and remove all the dams on the rivers and revert to the past - no matter the human cost.

The article (science) is based on captive RAISED fish which are not what is released into these rivers. By and large what are released are yoy/small fish who then grow up wild and their offspring (wild by definition) who are spawned in the rivers upon their return. To think that a parent fish in one or two generations change genetically so as to pass on that (bad) trait over and above those that have successfully developed over millions of years of survival evolution is nuts. Even if it were true those fish with the bad trait would be the first to be eaten and not survive to spawn. The science in the study is probably right but it does not lead to the conclusions the NYT makes for its own purposes. Their inferred conclusion being that the professional fisheries scientists at the hatcheries are destroying the rivers/fish for business purposes (greed). The truth is those fisheries scientists are doing a good job of (using the best methods in science to avoid any such problems [changing brood stock etc]) to carry out the public policies adopted by congress as an expression of the public will.

Off the soap-box for now.

ok here is link to pdf of original

http://oregonstate.edu/~blouinm/pdf_files/Araki_et_al_2007_Cons_Biol.pdf

he says hatcheries boost short term population with unknown affect on long term population (my summary)

Here are some findings from the study. Just as I thought they were ignored by the NYT. They show just the opposite result than that in the paper's article.



Furthermore, we have 3 years of data,

and combining probabilities across these three data sets

did not produce a significant result. Thus, it appears that

any difference between Hsupp fish and wild fish really is

slight.



So even by the most conservative

estimates, females taken into the hatchery should have

resulted in at least 4 to 10 times as many wild-born granddaughters

as females left in the wild.



But for the simple question of whether a supplementation

program can give a single-generation demographic boost

to a natural population of steelhead trout without obvious

short-term genetic consequences, the answer in this

case appears to be yes.



Steelhead from a supplementation hatchery (reared in a supplementation hatchery and then allowed to spawn

naturally in the wild) had reproductive success indistinguishable from that of wild fish.

Note the study did not deal with long term matters. They were not tested. As to that it simply does not attempt to make a finding.

At least we can see why the NYT ignored them.

I didn't want to go there, but I'm glad you did! I came this close >< to saying "consider the source" in my reply.

The entire study is moot anyway if the fisheries introduce wild genetics into the mix every year. I'm sure they do!

Bob thanks for your comment. I just do not like science being misrepresented for political purposes masquerading as the truth. It undermines all the scientists (their believability and reputations) out there working hard to learn the truth. The AFS mag recently had a couple articles on the serious effects the politicization of science has and a plea for the scientists to stick to peer reviewed work and not let the nuts influence them or their work.