The link takes you to an interesting article about the rapid domestication of salmon and how artificially bred fish, from wild parents, reproduce less well than naturally produced wild offspring.

'The researchers aren't yet sure what specific genetic changes occur in hatchery-born fish that make them ill-suited for reproduction in the wild'.

It's obvious to me that the survivors of an indoor clinical environment might not have survived in the wild, and the innate ability to recognise spawning cues, and carry out a complex series of manoeuvres that constitute successful spawning, might be lost very quickly.

So, don't stock trout into rivers.

Hatchery fish struggle to spawn in wild - Technology & science - Science - LiveScience - msnbc.com

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Well, if all this is to believed then in one single motion it kills off the argument that escapee farmed fish have a detrimental effect on the wild fish stocks through inter breeding.

It can't work both ways.

Hi', Warren. At a recent meeting, a 'Salmon Summit', I learned that even wild salmon when crossbred, male from one river system crossed with female from a different system, may produce progeny that survive pretty well in the hatchery. When released in each of the two 'parent streams' the two experimental 'strains' might survive in one or both locations, they might not. If released in a third river, there is a strong chance that the progeny batches will collapse. The modern advanced study of the genetics of Atlantic salmon reveals subtle differences in their genetic make-up which suit them ideally to a particular type of environment, the effects of evolution. The meeting learned that there were 7 different 'strains' of Atlantic salmon in Argyllshire alone, 4 in the catchment of Loch Awe. Cross-breeding with adults from streams in the same county could well result in a crash of the progeny planted out in, say, a tributary of the Tay.
We used to argue against throwing salmon parr at a river system in order to improve the runs, if the native stock was no longer self-perpetuating. It was argued, quite rightly, that if the environment was not up to scratch, releasing more parr would be a waste of money. My view on that used to be that if the indigenous stock was failing, what chance had a bunch of 'aliens?'
But is more subtle than that. It's not just a matter of clean water, good gravel and ample food; if the introduced stock does not match closely, genetically, with the native stock, the introduced fish stock might suffer a complete collapse.
In my area, the EA has been slanged unmercifully, for years, for not releasing as many parr as some salmon anglers thought they ought to introduce. I think the Ea has been justified in its caution in many instances. Dilution of the genetic pool is something against which some have argued for ages, and now it seems that scientific study has justified their fears. Jada

Are you suggesting that rivers that have been stocked in the past and their indigenous failing stock damaged with new genetics will never recover ?
Has it occurred to anyone that the offspring of these out crosses may well adapt genetically back to that river and therefore flourish after a small dip ?
Its seems to me that if you believe in wolves to dogs in one generation then you have to also agree with dogs to wolves in one generation?

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The word 'politics' is derived from the word 'poly', meaning 'many', and the word 'ticks', meaning 'blood sucking parasites'

Once again spot on.

Anyone who breeds lurchers will know this theory is pants.

Down here in southern England's chalkstream country where stocking with farmedbrown trout has been going on for well over 100 years there are some areas where a naturally recruited brown is a rarity. I won't call them "wild" because I'm not sure they are.

Now this could be a for a variety of reasons. Low flows, habitat degradation, siltation of spawning gravels, lack of cover for juveniles, predation, competition, the list is a long one. BUT it could also be that the trout in these rivers are no longer fitted to their environment. The problem is that we don't KNOW. We can speculate; we can apply the science; but as none of us are trout we don't know.

Chalk streams have always been low recruitment environments. That is why they were stocked in the first place. As prosperity and particularly mobility due to the rail network increased, more people were able to travel to and access these rivers, and the fishery could not be sustained through natural production. Various measures were tried to improve production; egg trays and cleaning the spawning gravels being two main means, but it was not enough. Stocking commenced and accelerated after the 1st World War when manpower shortages meant there were no longer the numbers of men around to be river keepers and agricultural workers.

It is these rivers which are most at risk from genetic modification. High recruitment rivers where there has historically been less need to stock have been less at risk. The science surrounding the Trout & Grayling Strategy relied heavily on the "precautionary principle" and was based on very limited studies. Even so, those studies did indicate that as little as three generations of farmed fish was sufficient to modify the behaviour and fitness of those fish. The American work has gone on for 19 years, and on that basis alone is much more robust.

However, we don't KNOW for sure, and that being the case have we the right to potentially cause irreversible damage to that which we purport to hold most dear?

In addition, only 3% survive their first winter. It only works one way; stock fish outcompete native fish and leave themselves. The net loss includes the fish meal needed to grow them, the abstraction for the farm and dishcharge of high suspended solids and large concentrations of pathogens.

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I can't believe that all hatchery fish are the same. If I run a small hatchery and take a couple of brownies for brood fish strip them and run the eggs into fry and then put them out in the spring, they are hatchery fish and one generation and they are inferior? Are you suggesting that if I grow some of them on to parr they will out compete the wild fish with all their superior 'river of birth' genetics?

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The word 'politics' is derived from the word 'poly', meaning 'many', and the word 'ticks', meaning 'blood sucking parasites'

I will go further. The deep substrate stream-side hatching boxes, that use eggs artificially stripped, either eyed or green, being even from wild caught fish, create a similar burden on the river by generating fish that don't spawn because they are not the product of natural spawning themselves. They might not displace in the same way when they are adult, having a better regard for river 'etiquette', but as they are less able to recognise spawning cues etc; they might as well be barren.

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Yes. Ever hatched fish? The natural propensity of trout to avoid each other is one of the greatest abilities it has. It enables a population to fill the river to the limit of the available territories. In a hatchery fish are not just kept together, they are stacked high. I believe that most of the innate desire to avoid each other is lost, permanently, before the babies leave the hatchery, let alone grow to fingerlings in earth ponds. They will, therefore, be bigger, stronger and could even be drawn to other year class members; smaller but infinately more important as wild fish 1+. The wild trout loses it territory and is displaced downstream.

__________________
http://141207.blogspot.com/
http://www.haddonestate.co.uk/rivers/rivers.php
http://www.thepeacockatrowsley.com/fishing.html