Releasing fish that have been maintained in captivity into a wild population
is something most people don't view as a big deal, or understand why there
is a problem there. This is especially true when the fish are released to
the original source population in the first place. After all, the fish
/came from/ there, whats the harm? Doesn't it even do good, replacing the
stock that was removed in the first place?
While on the surface, it seems to do no harm ... it can have potentially big
impacts. The fish in your pond (or someone elses aquarium) come from a
seperate population than the wild ones. How many sunfish did you start off?
How many bred and contributed to those fry you released? Were they
representative of the source population? How do you know? They may
represent inferior stock -- and, having been given a boost up thanks to
living in the cushy conditions of your pond, these inferior individuals have
flooded the gene pool. In the wild, less than 5% -- if that -- of any spawn
make it to year one. How much of your spawn, removed from predators did?
The 5% that make it are the best of the best -- no hump backs, no short or
long fins, just what Nature needs. The percent that made it from your pond,
on the other hand......
Second, captive fish learn captive habits. Even stocked trout behave
differently than wild raised -- they're easier to catch, for one. Studies
have also shown that they have higher predator mortality. They see the
Great Blue Heron and come rushing over, expecting trout pellets. No dice.
Beyond feeding, captive fish are often in the open more, may have poorer
parenting skills (look-in-whats happened to soem tropicals that don't even
raise their own young anymore), etc. WORSE, captive fish "teach" bad habits
to wild fish. Think about it -- if you have a school of wild caught fish
that aren't eating, throw in some zebra danios. The zebra danios "teach"
the wild fish to eat prepared foods. If you have shy fish, add some dither
fish -- they make them come out. The same happens in the wild, your
"stupid" captive fish start sharing their bad habits. This has been shown
to happen with farmed salmon escaping into the wild.
So when you release fry from a captive population, you're degrading the
natural population. And to make matters worse, you don't know what else
you're transmitting to the wild population. Have you ever, ever seen a wild
caught fish with Ich? Disease and parasites live-in-fairly low densities in
the wild (with some exceptions) -- they live in high densities in captivity,
even when they're not showing up on the fish. Your sunfish are probably a
great source population of Ich parasites and who knows what else.
So, why does the DNR stock fish? How come they can get away with it? Well,
as I mentioned above, hatchery fish are a problem. We've seen some genetic
shifts due to hatchery stockings. They're also generally stocking fish that
are otherwise in trouble, either from fishing, from a rotenone episode,
whatever.... bad fish are better than no fish. They're answering the supply
and demand problem in some cases.
Perhaps the most marked reason for not releasing a fish: When someone else
sees or hears about you dumping fish into a stream, they may not note the
difference between releasing a sunfish from its original population back in,
they simply know that you dumped fish. They may repeat it, with something
not native.
Oh, and it also may be illegal.:)
--
end
____^___
><,DARWIN,>
Joshua L. Wiegert
AIM UID: JoshuaWiegert Yahoo:
JLW_DUNE_NET
HTTP://WWW.NATIVEFISH.ORG/JWiegert/index.html
Feel free to contact me by any of the above means for any reason.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=--=-=-=-=-=-=-=-=-=-=-=-=-=-=
----- Original Message -----
From: "George W Corben" <gwcorben-in-juno.com>
To: <nanfa-l-in-nanfa.org>
Sent: Tuesday, November 01, 2005 10:32 AM
Subject: Re: NANFA-L-- Final 2005 Water garden Sunfish tally
> The Creek chubs were among a dozen small 1/2" fry that I netted from the
> shallow margin of a
> large washout below the Lake Olathe spillway. I also collected a Orange
> Throat darter and 2 small
> crayfish from the same location that same day in late May.
> All of my Green Sunfish and most of the Longears were caught in minnow
> traps baited with canned
> catfood in Aug 2004 in the same area of Cedar Creek. Luke McClurg
> provided me with 4 Orange
> spotted and 4 Longears from Jefferson & Wabaunsee County to the west of
> me.
> All of this years Longear and 52 Green Sunfish fry went to water
> gardens/ponds here in the KC area.
> The remaining Greens were released back into Cedar Creek-in-the same
> location their parents came from
> Also the adult Greens like wise.
> I had 5 Longear and 3 Green nests in June and July but the Greens proved
> to be much more prolific.
>
> George.
> /-----------------------------------------------------------------------
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/ visit http://www.nanfa.org Please make sure all posts to nanfa-l are
/ consistent with the guidelines as per
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