{press release from Oregon State University}

The impact of hatcheries on salmonids is so profound that in just one generation traits are selected that allow fish to survive and prosper in the hatchery environment, at the cost of their ability to thrive and reproduce in a wild environment.

The findings, published in December's Proceedings of the National Academy of Sciences, show a speed of evolution and natural selection that surprised researchers.

They confirmed that a primary impact of hatcheries is a change in fish genetics, as opposed to a temporary environmental effect.

“We’ve known for some time that hatchery-born fish are less successful at survival and reproduction in the wild,” said Michael Blouin, a professor of zoology at Oregon State University. “However, until now, it wasn’t clear why. What this study shows is that intense evolutionary pressures in the hatchery rapidly select for fish that excel there, at the expense of their reproductive success in the wild.”

Hatcheries are efficient at producing fish for harvest, the researchers said, but this and other studies continue to raise concerns about the genetic impacts that hatchery fish may have when they interbreed with wild salmon and steelhead, and whether or not they will help wild salmonid runs to recover.

These findings were based on a 19-year genetic analysis of steelhead in Oregon’s Hood River. It examined why hatchery fish struggle to reproduce in wild river conditions, a fact that has been made clear in previous research. Some of the possible causes explored were environmental effects of captive rearing, inbreeding among close relatives, and unintentional “domestication selection,” or the ability of some fish to adapt to the unique hatchery environment.

The study confirmed that domestication selection was at work.
When thousands of smolts are born in the artificial environment of a hatchery, those that survive best are the ones that can deal, for whatever reason, with hatchery conditions. But the same traits that help them in the hatchery backfire when they return to a wild river, where their ability to produce surviving offspring is much reduced.

“We expected to see some of these changes after multiple generations,” said Mark Christie, an OSU post-doctoral research associate and lead author on the study. “To see these changes happen in a single generation was amazing. Evolutionary change doesn’t always take thousands of years.”
It’s not clear exactly what traits are being selected for among the thousands of smolts born in hatcheries, the scientists said, but one of the leading candidates is the ability to tolerate extreme crowding. If research can determine exactly what aspect of hatchery operations is selecting for fish with less fitness in the wild, it could be possible to make changes that would help address the problem, they said.

Historically, hatchery managers preferred to use fish born in hatcheries as brood stock to create future generations, because whatever trait they had that allowed them to succeed in the hatchery helped produce thousands of apparently healthy young salmon. But they later found that when those same fish were released they had a survival and reproductive success that was far lower than those born in the wild.

Billions of captive-reared salmon are intentionally released into the wild each year in order to increase fishery yields and bolster declining populations. The steelhead studied in this research are, in fact, listed as threatened under the Endangered Species Act, and part of their recovery plan includes supplementation with hatchery fish.

“It remains to be seen whether results from this one study on steelhead generalize to other hatcheries or salmon species,” Blouin said.
“Nevertheless, this shows that hatcheries can produce fish that are genetically different from wild fish, and that it can happen extraordinarily fast,” he said. “The challenge now is to identify the traits under selection to see if we can slow that rate of domestication.”

Biggest load of keech I've read in quite some time.


"intense evolutionary pressures in the hatchery!"

Have you ever heard such rubbish?

And this notion about domesticated fish baffles me too. How do you domesticate a fish?

Wild fish are be better at surviving in the wild, that is undeniable.

Maybe this study of immediate selection will not generalise, but gradual selection will happen. I have an open mind on the idea that hatcheries could do long term harm.

If a hatchery closed maybe the wild natural selection would reverse the genetic effects of the hatchery. If that's the case, then a hatchery wouldn't be very harmful in the long run.

The effect of hatcheries is a subject that needs to be considered.

The major reason for a reduction in genetic diversity of hatchery fish is simply due to the narrow gene pool from which the fish are hatched.

If you take 10 wild steelhead/salmon, from a wild population of x1,000, we can assume that they are not related (to try and ensure a hypothetical maximal genetic differentiation between individuals). If you then breed from these fish (strip, milt, hatch), you start with an effective population size of 10 individuals. Any evolutionary biologist will confirm that an effective population size of 10 is exceptionally low. Of course there is going to be a change in fish genetics (relative to wild stock)! A large number of spawned fish that are very similar genetically. It is the act of removing brood stock from the wider gene pool that has the major impact on narrowing genetic diversity, especially if these same fish continue to be bred from without introducing 'new' genetic material each generation.

For traits that benefit hatchery fish to be selected 'in one generation' suggests that a VERY large number of the young fish in hatcheries must die, there is no other way they can be selected in one generation. If these same fish are bred from, it is perfectly plausible that over a few generations of inbreeding, your effective population size would be down to 2 or 3 individuals. This means, in principal, that you are releasing 100s or 1000s of near genetically identical fish into a river, expecting them to survive well and breed. The odds of these individuals, having been rearered in brood cages, still having the optimal compliment of alleles (genes) that allow them to successfully exploit the environment they have just been released into is hopeful at the best, but statistically exceptionally unlikely.

In short, of course, if you breed more than one generation of salmonids in brood cages, and you get more than minimal mortality, you are introducing genetically weaker fish (for that given environment).

Nick

Hand feeding or from a machine on a timer. Therefore no real competition for food allowing the strongest and fittest to survive naturally.

No predatures.

No extreme river/weather conditions.

Surely the only way that a hatchery reared fish can in any way interfere with the genetic strain in the river would be to (assuming they are hatched from adults taken from the river in question)

feed and survive in the river

smolt and feed and survive in the sea

make the return journey to the river

make its way to the spawning ground

successfully spawn with another fish

having acheived all that how are they inferior?

escapees from cages are another matter

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

There you have the ‘stocking’ dilemma in a nut shell.

The closer the life cycle ‘stage’ to an adult when you stock the more damage you may impart on the genetics (having 'short-cut' natural selection) - yet the higher % will return - and therefore the greater the temptation to do so.

This really is all about understanding the risks and only when the 'point' is reached where the risk is worth taking should it be taken. I guess it is that 'point' that people dont agree on!

Additionally I would be interested to know if the reverse is also true i.e. the salmon evolve to wild type fish within one generation ? Of course we wouldn't be able to tell which ones they are as they don't evolve the missing adipose fin and if their genetics have reverted to the same as wild fish then they will be ...wild fish

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

That fish behaves exactly the same as it would in the wild, if it were ever born in the wild that is.

Folks fish do not change behaviour because they're ranched or farmed.

They still do whatever they would do in the wild.

The notion of a 'domesticated' fish being any lesser than a wild fish is preposterous, as is proved when escapee salmonids ruin our rivers to spawn.

---------- Post added at 05:56 PM ---------- Previous post was at 05:54 PM ----------

What do you mean genetics reverted to the same as wild fish?

Some of you seem to think the gentotypes of fish suddenly change when when the fish is farm reared. Why?