Stocked fish...

peter crabtree · #1 (**permalink**) 10-02-2012, 14:26

The E.A. are stocking many rivers with silverfish reared at their Calverton farm. Do you think these fish have the same instincts as wild fish after being hand reared before release. We often hear of hand reared animals in zoos which would not survive if released into the wild, is it the same with these fish?

beerweasel · #2 (**permalink**) 10-02-2012, 14:37

Nearly everything a Roach does is instinct, whereas most Mammals learn from their parents.
I'm sure within a week they would be feral.

mol · #3 (**permalink**) 10-02-2012, 14:44

Gotta agree with beerweasal.

You could possible agrue that even if they're naive and end up going down the throats of predators then it's less pressure on wild fish stocks and will in turn help boost wild fish stocks.

barbelboi · #4 (**permalink**) 10-02-2012, 14:54

As BW says, and I believe the general direction of thought is 'it will normally take between one to two weeks'. It seems logical to me.
Jerry

S-Kippy · #5 (**permalink**) 10-02-2012, 17:56

If they last that long !

waggy · #6 (**permalink**) 10-02-2012, 18:32

Quote:

Originally Posted by peter crabtree

The E.A. are stocking many rivers with silverfish reared at their Calverton farm. Do you think these fish have the same instincts as wild fish after being hand reared before release. We often hear of hand reared animals in zoos which would not survive if released into the wild, is it the same with these fish?

If they have not been selectively bred then of course they are still wild type fish and have their instincts intact. But if you're asking whether they can adapt to and thrive on a different prey suite in enough abundance in different water conditions then the answer is a small proportion of them will probably survive. That's what natural selection is all about - which of the many will be eaten, etc and which few will manage to combat predation, starvation, etc.
In the normal course of events, selective factors will decide how many and which ones.

---------- Post added at 12:32 ---------- Previous post was at 12:30 ----------

Quote:

Originally Posted by beerweasel

Nearly everything a Roach does is instinct, whereas most Mammals learn from their parents.
I'm sure within a week they would be feral.

It's instinct in both cases, beerweasel.

terry m · #7 (**permalink**) 10-02-2012, 20:15

Surely in the case of mammals it is conditioned reflex?

geoffmaynard · #8 (**permalink**) 10-02-2012, 20:37

I find it strange that when dealing with salmon, the EA insist that hatchery fish must be be kept separate from wild fish to preserve something they call 'genetic integrity' - yet when stocking with coarse fish it seems that any old mongrel from Calverton will do. Why is this?

It would seem to me on the surface that a mongrel breed will strengthen the genetic integrity of a species by breeding with the wild fish - and this salmon breeding tactic results in in-breeding. With most creatures this is well-known to produce genetic flaws.

So - anyone out there got any answers? Why this double standard Messer EA ??

Jeff Woodhouse · #9 (**permalink**) 10-02-2012, 21:12

Quote:

Originally Posted by geoffmaynard

Why is this?

Can't say for salmon, but where trout are concerned I did ask some years ago if the Thames could be restocked with some nice brown trout of around 6". 'No good' they said, the fish wouldn't last and would never be like feral fish, but the answer is to put trout eggs in a bubbler on the weir. As the eggs hatch they work their way up through the stones in the bubbler and when they spew out of the top they are more like feral fish and their chances of survival are that much better.

So I asked for a bubbler. And I am still waiting 8 years later.

The first lots of barbel, 10,000 in all, that were introduced to the Thames in late '99/2000 were off Trent stock, I believe. Subsequent stockings have been from Thames fish, so I'm told.

Bill Wilson · #10 (**permalink**) 10-02-2012, 23:59

- this has been the subject of a lot research - this paper may partially answer the initial question:
Movements and habitat use of wild and stocked juvenile chub, Leuciscus cephalus (L.), in a small lowland river - BOLLAND - 2008 - Fisheries Management and Ecology - Wiley Online Library

- This study raises the question as to whether stocking with coarse fish is beneficial or more of a PR exercise by the EA when funds are lacking for resoration/rehabilitation schemes:
http://onlinelibrary.wiley.com/doi/1...4.00394.x/full