rw wrote:
Willi wrote:


I disagree. IMO, by carefully managing hatcheries the result can be
more natural, but hatchery produced fish will always be different than
naturally spawned wild fish. Hatcheries are a last resort for
restoring native, wild fish populations.


I agree with you, Willi, but with the caveat that I think hatcheries
could be much more effective than they are now, but it would cost money.
I suspect that a big problem (maybe THE problem) is that the fish that
are raised and survive in hatcheries are those best adapted to hatchery
conditions, which are very benign compared to wild conditions. They
don't have to deal with predators, weather and water conditions, and
diseases in the same way that wild fish do. In the end, you get a cohort
of fish that hasn't been culled by natural conditions, so there is a
"drift" of their genetics toward adaptation to man-made hatchery
conditions.

In principle, these problems could be addressed by more natural
conditions in the hatchery, but the cost would be very high.


I don't get your point. If these "natural" conditions were reproduced in
the hatcheries, the resulting mortality would be the same as in stream
bred fish. If that's the case, why not just use the stream as the
hatchery. Instead of spending money on the hatchery and the fish for
stocking, use the money to improve the conditions for natural reproduction.

I seeing stocking as having two main uses:

1. To provide a put and take fishery in places where natural
reproduction isn't possible (However, in cases like that I question if
the fish being stocked belong in those waters)


2. As a stop gap method to supplement or reintroduce a native fish
population. If this needs to be an ongoing program, something is wrong
with the fishes' environment and that needs to be addressed if the
fishery is ever going to change from a man made one to a natural self
sustaining one. Supplementing hatchery stock on top of a naturally
reproducing population of the species of fish causes lots of problems.
In many cases it the reduces the reproduction success of the stream bred
fishes.

Willi