Releasing Native Fish?

[wormsburp]

I have been considering keeping some native fish, but I was wondering
about releasing them once they get large. Usually I would say don't put
anything into the local water, but if it came from there, can it go
back there? If you would discourage this, is it because it can't be
done or because it is often done badly?

[dfreas]

This depends very much on the specifics of your situation. There are
areas in which this would be a very bad idea, and others where it
wouldn't matter a bit. For instance if you catch a catfish out of, say,
the James river in VA and then return it two years later - that would
be fine. OTOH if you went just a tiny bit farther north to the Potomac
river in MD and caught a Snakehead fish, kept it for two years and then
returned it that would be VERY VERY BAD.

Check your local regulations first and then if it's still ok be sure to
use common sense. Don't collect anything from wildlife preserves or
wetland areas and deffinately don't return anything to those areas. Be
sure to return your fish to the same place you collect it from. Don't
collect a baby predatory fish and then feed it beefheart for several
years and return it to the water as a four foot monster that will
immediately wipe out all of the other fish in the area.

Be sure not to collect anything you can't take care of. I've rasied
wild caught baby catfish from under an inch to about 6" without any
problem - they eat anything and tolerate a wide range of conditions.
Baby Largemouth Bass are much more difficult - they're picky eaters and
seem to be susceptable to disease in aquaria. Be ready to return
anything you collect within a few days if it obviously isn't going to
work out.

Lastly, going back to the regulations - your state may require you to
have a fishing license to collect fish. Even though you only want one
or two and have no intention of eating them many states still call this
"fishing" so if you don't have a license check to see if you need one
in your state.

Good luck - going on a collection run is infinitely more fun than going
to the LFS!

-Daniel

[NetMax]

"dfreas" > wrote in message
ups.com...
> This depends very much on the specifics of your situation. There are
> areas in which this would be a very bad idea, and others where it
> wouldn't matter a bit. For instance if you catch a catfish out of, say,
> the James river in VA and then return it two years later - that would
> be fine. OTOH if you went just a tiny bit farther north to the Potomac
> river in MD and caught a Snakehead fish, kept it for two years and then
> returned it that would be VERY VERY BAD.
>
> Check your local regulations first and then if it's still ok be sure to
> use common sense. Don't collect anything from wildlife preserves or
> wetland areas and deffinately don't return anything to those areas. Be
> sure to return your fish to the same place you collect it from. Don't
> collect a baby predatory fish and then feed it beefheart for several
> years and return it to the water as a four foot monster that will
> immediately wipe out all of the other fish in the area.
>
> Be sure not to collect anything you can't take care of. I've rasied
> wild caught baby catfish from under an inch to about 6" without any
> problem - they eat anything and tolerate a wide range of conditions.
> Baby Largemouth Bass are much more difficult - they're picky eaters and
> seem to be susceptable to disease in aquaria. Be ready to return
> anything you collect within a few days if it obviously isn't going to
> work out.
>
> Lastly, going back to the regulations - your state may require you to
> have a fishing license to collect fish. Even though you only want one
> or two and have no intention of eating them many states still call this
> "fishing" so if you don't have a license check to see if you need one
> in your state.
>
> Good luck - going on a collection run is infinitely more fun than going
> to the LFS!
>
> -Daniel


Also if the native fish will be kept in proximity to tropical fish, then
there is a danger of cross-contamination (ie: through nets, filters etc),
then this could be very bad for the environment either was released into.
--
www.NetMax.tk

[dfreas]

Good point - I hadn't thought of that since I usually keep my natives
in native only tanks. Makes for easier upkeep that way. Also I've found
that native fish tend to be hardier than tropicals and have a tendancy
to eat the tropicals you keep them with.

-Daniel

[Mean_Chlorine]

Thusly "wormsburp" > Spake Unto All:

>I have been considering keeping some native fish, but I was wondering
>about releasing them once they get large. Usually I would say don't put
>anything into the local water, but if it came from there, can it go
>back there? If you would discourage this, is it because it can't be
>done or because it is often done badly?

I wouldn't have any problem with this provided they go back into the
very body of water from which they came. Do NOT release a 'native'
fish from one area into a new water - it is then every bit as much an
invasive species as goldfish or oscars in Florida are, and can have
every bit as deleterious effect on the local wildlife.
There are examples of translocated 'native' species killing off local
'native' species.

[Keith]

Some thoughts on releasing native fish-

Although I don't think it's that big of a deal if you have to treat the
fish for a disease and then release them, some medications do specify
not to use on food fish. Like I said, I don't think it's that big of a
deal, but it may be something to consider.

If you're wanting to keep native fish, why not stick with darters and
other "minnows". These fish stay relatively small and can be kept for
many years. I don't think it's fair to the fish to keep them in a tank
until they're too big and then release them back into the wild. They
have mostly instinct to catch their prey, but also a lot of practice.
To feed them goldfish is not the same as releasing them and expecting
them to find their food on their own. It's like getting a German
shepherd (which you know will be a large dog), raising him, and then
when he's no longer "puppy-like", giving him to an animal shelter or to
a rescue group. It is my opinion that you should be prepared to care
for your fish for the life of the fish, and if you are not going to be
able to, consider not keeping those fish and get something different.

Make sure that you know the water requirements of the natives you are
planning on keeping. Many native fish (at least farther north) prefer
cooler temperatures than your tropical fish. One way to keep the tank
cool is to purchase a chiller. While these are usually out of our
price ranges, you can also try purchasing power heads to circulate the
water to help cool it off.

Finally, I think native fish tanks are awesome. Although I've not kept
one yet, I will probably do so in the future. Just make sure you do
your research. Know the requirements and know your fish. There are
many of these smaller fish that are endangered. Not only is keeping
them illegal, but can also be detrimental to the population.

Be sure to look around on the web: there are message boards and
websites dedicated to keeping natives. And (as has been stressed in
the previous messages) be sure to check with local regulations on
keeping and capturing natives.

Keith

[Rocco Moretti]

wormsburp wrote:
> I have been considering keeping some native fish, but I was wondering
> about releasing them once they get large. Usually I would say don't put
> anything into the local water, but if it came from there, can it go
> back there? If you would discourage this, is it because it can't be
> done or because it is often done badly?

Don't ask us - we don't know where you live, and more importantly, what
the local laws are.

Contact your local department of natural resources. Where I live it is
the state agency which issues sport fishing licenses, and also manages
the fish hatcheries for local river/lake stocking. They should be able
to tell you what the local laws are about releasing fish into waterways
are in your area. More importantly, if your area runs a fish hatchery
program, and you get the number for the technical/scientific people who
actually manage it (as opposed to the bureaucrats at the capitol), they
can give you guidelines or hints as to whether it's a good idea, even if
it is legal. Heck, you might even be able to obtain some eggs/young fish
from them directly.

[Rich]

"dfreas" > wrote in message
ups.com...
> This depends very much on the specifics of your situation. There are
> areas in which this would be a very bad idea, and others where it
> wouldn't matter a bit. For instance if you catch a catfish out of, say,
> the James river in VA and then return it two years later - that would
> be fine. OTOH if you went just a tiny bit farther north to the Potomac
> river in MD and caught a Snakehead fish, kept it for two years and then
> returned it that would be VERY VERY BAD.

As an interested fishkeeper from across the pond, out of curiosity, why
would it be bad ?
Rich

[dfreas]

They are an introduced species of predatory fish that have no known
predators in the Chesapeake area rivers (Which would be Maryland and
Virginia for the most part). In recent years they have been popping up
in the Potomac and are considered destructive to local ecosystems.
Anyone that catches one is supposed to kill it and report the catch to
the state authorities. Here are a few quotes from the local department
of game and inland fisheries:

"In 2002, the Board of Game and Inland Fisheries added the snakehead
fish to the list of predatory and undesirable exotic species, making it
illegal to possess a snakehead fish in Virginia without a permit issued
by the Department of Game and Inland Fisheries. Federal regulations
enacted in October 2002 prohibit the importation of snakehead fish into
the United States and prohibit interstate transport of these animals.
Individuals who still own a snakehead need to contact the Department of
Game and Inland Fisheries immediately for proper disposal of the fish."

"... Additionally, the Department of Game and Inland Fisheries'
Snakehead Fish Incident Management Team, which includes members of
fisheries, wildlife diversity, law enforcement, and public information
programs, was formed to coordinate all aspects of Virginia's response
to this issue. Members of the team consult regularly with national
experts and other agencies/organizations to determine the full extent
and implications of the situation."

"Northern snakehead fish are not known to attack humans. Nonetheless,
these animals present considerable threats to our native wildlife and
ecosystems, since they have no natural predators in our waters."

For more information take a look at the Virginia Department of Game and
Inland Fisheries website:
http://www.dgif.state.va.us/fishing/snakeheads.html

So that's why it would be bad :-)

-Daniel

[Elaine T]

dfreas wrote:
> They are an introduced species of predatory fish that have no known
> predators in the Chesapeake area rivers (Which would be Maryland and
> Virginia for the most part). In recent years they have been popping up
> in the Potomac and are considered destructive to local ecosystems.
> Anyone that catches one is supposed to kill it and report the catch to
> the state authorities. Here are a few quotes from the local department
> of game and inland fisheries:
>
> "In 2002, the Board of Game and Inland Fisheries added the snakehead
> fish to the list of predatory and undesirable exotic species, making it
> illegal to possess a snakehead fish in Virginia without a permit issued
> by the Department of Game and Inland Fisheries. Federal regulations
> enacted in October 2002 prohibit the importation of snakehead fish into
> the United States and prohibit interstate transport of these animals.
> Individuals who still own a snakehead need to contact the Department of
> Game and Inland Fisheries immediately for proper disposal of the fish."
>
> "... Additionally, the Department of Game and Inland Fisheries'
> Snakehead Fish Incident Management Team, which includes members of
> fisheries, wildlife diversity, law enforcement, and public information
> programs, was formed to coordinate all aspects of Virginia's response
> to this issue. Members of the team consult regularly with national
> experts and other agencies/organizations to determine the full extent
> and implications of the situation."
>
> "Northern snakehead fish are not known to attack humans. Nonetheless,
> these animals present considerable threats to our native wildlife and
> ecosystems, since they have no natural predators in our waters."
>
> For more information take a look at the Virginia Department of Game and
> Inland Fisheries website:
> http://www.dgif.state.va.us/fishing/snakeheads.html
>
> So that's why it would be bad :-)
>
> -Daniel
>
To give you an idea of snakeheads, the fish store I worked for used to
sell them. If you toss a few feeder goldfish into a tank of oscars, the
oscars calmly swim over and eat them (our oscars were well-fed). If you
toss a few feeder goldfish into a tank of mid-sized pirhanas, they're
torn apart, but you could see what happened. If you toss a few feeder
goldfish into a tank of even tiny snakeheads, there is a blur of silver,
goldfish scales fly, and the tank returns to normal in a fraction of a
second.

Snakeheads can grow to 2-3 feet depending on the species and are fast,
vicious, powerful predators. Hungry snakeheads can crack the glass of
small tanks so we usually recommended thick glass or acrylic. Every now
and again, we'd get a 2 foot snakehead back to the store in a bucket
because it had eaten every other fish in the owner's tank or cracked the
glass of its inappropriately small tank. We were always glad to get
them back because if released in non-native waters, like anywhere in the
US, snakeheads pretty much eat everything in sight.

In their native areas (India, Malaysia, China, Thailand, Korea),
snakeheads are favored as a food fish because they can stay alive and
fresh for many hours out of water using a labyrinth organ.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><

[perrin]

Agree with you on the speed of their attacks, Elaine.

I'm curious, I'm not from the States. Is there any fish there (or in your
region) that can stand up to snakeheads? The bigger American cichlids should
do fine I suppose? Any land-based or amphibous predators?

I have heard about walking catfish being a threat to the ecosystem there but
that has turned out to be a red herring, so just want to be clearer about
snakeheads. Of course I'm aware that walkers are not predatory fish but
snakeheads are.

cheers
perrin


"Elaine T" > wrote in message
m...
: dfreas wrote:
: > They are an introduced species of predatory fish that have no known
: > predators in the Chesapeake area rivers (Which would be Maryland and
: > Virginia for the most part). In recent years they have been popping up
: > in the Potomac and are considered destructive to local ecosystems.
: > Anyone that catches one is supposed to kill it and report the catch to
: > the state authorities. Here are a few quotes from the local department
: > of game and inland fisheries:
: >
: > "In 2002, the Board of Game and Inland Fisheries added the snakehead
: > fish to the list of predatory and undesirable exotic species, making it
: > illegal to possess a snakehead fish in Virginia without a permit issued
: > by the Department of Game and Inland Fisheries. Federal regulations
: > enacted in October 2002 prohibit the importation of snakehead fish into
: > the United States and prohibit interstate transport of these animals.
: > Individuals who still own a snakehead need to contact the Department of
: > Game and Inland Fisheries immediately for proper disposal of the fish."
: >
: > "... Additionally, the Department of Game and Inland Fisheries'
: > Snakehead Fish Incident Management Team, which includes members of
: > fisheries, wildlife diversity, law enforcement, and public information
: > programs, was formed to coordinate all aspects of Virginia's response
: > to this issue. Members of the team consult regularly with national
: > experts and other agencies/organizations to determine the full extent
: > and implications of the situation."
: >
: > "Northern snakehead fish are not known to attack humans. Nonetheless,
: > these animals present considerable threats to our native wildlife and
: > ecosystems, since they have no natural predators in our waters."
: >
: > For more information take a look at the Virginia Department of Game and
: > Inland Fisheries website:
: > http://www.dgif.state.va.us/fishing/snakeheads.html
: >
: > So that's why it would be bad :-)
: >
: > -Daniel
: >
: To give you an idea of snakeheads, the fish store I worked for used to
: sell them. If you toss a few feeder goldfish into a tank of oscars, the
: oscars calmly swim over and eat them (our oscars were well-fed). If you
: toss a few feeder goldfish into a tank of mid-sized pirhanas, they're
: torn apart, but you could see what happened. If you toss a few feeder
: goldfish into a tank of even tiny snakeheads, there is a blur of silver,
: goldfish scales fly, and the tank returns to normal in a fraction of a
: second.
:
: Snakeheads can grow to 2-3 feet depending on the species and are fast,
: vicious, powerful predators. Hungry snakeheads can crack the glass of
: small tanks so we usually recommended thick glass or acrylic. Every now
: and again, we'd get a 2 foot snakehead back to the store in a bucket
: because it had eaten every other fish in the owner's tank or cracked the
: glass of its inappropriately small tank. We were always glad to get
: them back because if released in non-native waters, like anywhere in the
: US, snakeheads pretty much eat everything in sight.
:
: In their native areas (India, Malaysia, China, Thailand, Korea),
: snakeheads are favored as a food fish because they can stay alive and
: fresh for many hours out of water using a labyrinth organ.
:
: --
: __ Elaine T __
: ><__'> http://eethomp.com/fish.html <'__><

[dfreas]

Wow. I've never actually seen a snakehead in action - only read about
them at the website I provided the first time I decided to do a local
tank and wanted to go collecting. I had no idea they were that fierce.
Sounds like it would be a cool fish to own if I had unlimited
resources.....alas for that....

-Daniel

[Elaine T]

perrin wrote:
> Agree with you on the speed of their attacks, Elaine.
>
> I'm curious, I'm not from the States. Is there any fish there (or in your
> region) that can stand up to snakeheads? The bigger American cichlids should
> do fine I suppose? Any land-based or amphibous predators?
>
> I have heard about walking catfish being a threat to the ecosystem there but
> that has turned out to be a red herring, so just want to be clearer about
> snakeheads. Of course I'm aware that walkers are not predatory fish but
> snakeheads are.
>
> cheers
> perrin
>
I did a little more digging and found that temperate snakeheads like the
Northern snakehead have definately bred successfully here. There are
other large native predatory fish here like bass, bluefish, bowfin, and
gars competing for the same niche in the ecosystem. Those fish would
"stand up" to snakeheads but nothing here would prey on them except
perhaps gators and crocodiles in Florida. Bears and eagles fish as
well, but I doubt they would favour snakeheads over any other large fish.

The main concerns are that the snakeheads might outcompete the native
fish or introduce pathogens to local fish populations. The concern
seems reasonable given that they are still being found in native waters.
I don't think they'll be the kudzu of the fish world, but I do think
they could establish as another top predator if releases continue.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><
rec.aquaria.* FAQ http://faq.thekrib.com

[Elaine T]

dfreas wrote:
> Wow. I've never actually seen a snakehead in action - only read about
> them at the website I provided the first time I decided to do a local
> tank and wanted to go collecting. I had no idea they were that fierce.
> Sounds like it would be a cool fish to own if I had unlimited
> resources.....alas for that....
>
> -Daniel
>
They were interesting, that's for sure. The food disappearing act was
always fun to watch, but after a while I found it more fun to watch the
customers. We used to get these guys into the store wearing fancy
jogging suits, high top sneakers, bunches of gold jewellery, and
carrying big wads of cash who would say "give me the meanest fish you've
got" or "I want a fish that eats other fish." I'd take them to the
unlikely looking tank of baby snakeheads and drop in a goldfish. They'd
buy one nine times out of ten.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><
rec.aquaria.* FAQ http://faq.thekrib.com

[perrin]

Thanks for the reply (and research). Gars are also kept where I live
(Singapore) and they are also strong predators. IMHO a predatory fish
doesn't just "take over" or "ruin" an eco-system because of its ferocity or
hardiness - is there, for instance, something about the snakehead's
reproduction that makes it a serious threat? Animal migration and movement
have been part and parcel of evolution and there's no eco-system that's
self-contained or autonomous. I wonder if there's a bit of hysteria in the
fear over foreign/imported fish in the US.

Just my opinion - feel free to enlighten me - not trying to stir up a
hornet's nest here.

"Elaine T" > wrote in message
m...
: perrin wrote:
: > Agree with you on the speed of their attacks, Elaine.
: >
: > I'm curious, I'm not from the States. Is there any fish there (or in
your
: > region) that can stand up to snakeheads? The bigger American cichlids
should
: > do fine I suppose? Any land-based or amphibous predators?
: >
: > I have heard about walking catfish being a threat to the ecosystem there
but
: > that has turned out to be a red herring, so just want to be clearer
about
: > snakeheads. Of course I'm aware that walkers are not predatory fish but
: > snakeheads are.
: >
: > cheers
: > perrin
: >
: I did a little more digging and found that temperate snakeheads like the
: Northern snakehead have definately bred successfully here. There are
: other large native predatory fish here like bass, bluefish, bowfin, and
: gars competing for the same niche in the ecosystem. Those fish would
: "stand up" to snakeheads but nothing here would prey on them except
: perhaps gators and crocodiles in Florida. Bears and eagles fish as
: well, but I doubt they would favour snakeheads over any other large fish.
:
: The main concerns are that the snakeheads might outcompete the native
: fish or introduce pathogens to local fish populations. The concern
: seems reasonable given that they are still being found in native waters.
: I don't think they'll be the kudzu of the fish world, but I do think
: they could establish as another top predator if releases continue.
:
: --
: __ Elaine T __
: ><__'> http://eethomp.com/fish.html <'__><
: rec.aquaria.* FAQ http://faq.thekrib.com

[Mean_Chlorine]

Thusly "perrin" > Spake Unto All:

>reproduction that makes it a serious threat? Animal migration and movement
>have been part and parcel of evolution and there's no eco-system that's
>self-contained or autonomous. I wonder if there's a bit of hysteria in the
>fear over foreign/imported fish in the US.
>
>Just my opinion - feel free to enlighten me - not trying to stir up a
>hornet's nest here.

Your local ecosystem in Singapore is a nice example of what can
happen. About four fifths of your indigenous freshwater species are
now extinct or endangered, replaced mainly by released aquarium fish.
Basically, there's only isolated pockets left of your original
ecosystem.

It is not at all so that it is only big predators that are a threat -
any new species will compete in some way with the old species, for
food, for territory, for caves... In the vast majority of cases the
introductions fail. It has been estimated that more than 99% of all
introductions lead to the extinction of the introduced species, as the
become outcompeted by the local species, who have the advantage of
'home court'.

In nearly all the remaining cases, the newly introduced species
becomes a part of the ecosystem without causing a big upset.

However, in some cases a new arrival will replace a local species,
marginalizing it or driving it into extinction. It does happen. It has
happened.
That it doesn't happen *often* isn't really a defence.

[perrin]

Or the new species will find an equilibrium with the existing species,
within the eco-system. That seems to have been the case with the walking
catfish, also released in the States. It was feared for its voracious
appetite, hardiness, ability to walk onland (and spread) and reproduce
quickly. It seems now that the hysteria was due to a basic misunderstanding
of what the fish is - how much of a predator was it?

My point is this, Mike - I'd like to understand how the eco-system copes
with the new fish. I'm not saying that the dreaded scenario of replacement
won't happen but I'd like to understand what happens in the majority of
situation when the new fish is contained.

Btw, any more info on snakeheads - reproduction?

cheers
perrin

"Mean_Chlorine" > wrote in message
...
: Thusly "perrin" > Spake Unto All:
:
: >reproduction that makes it a serious threat? Animal migration and
movement
: >have been part and parcel of evolution and there's no eco-system that's
: >self-contained or autonomous. I wonder if there's a bit of hysteria in
the
: >fear over foreign/imported fish in the US.
: >
: >Just my opinion - feel free to enlighten me - not trying to stir up a
: >hornet's nest here.
:
: Your local ecosystem in Singapore is a nice example of what can
: happen. About four fifths of your indigenous freshwater species are
: now extinct or endangered, replaced mainly by released aquarium fish.
: Basically, there's only isolated pockets left of your original
: ecosystem.
:
: It is not at all so that it is only big predators that are a threat -
: any new species will compete in some way with the old species, for
: food, for territory, for caves... In the vast majority of cases the
: introductions fail. It has been estimated that more than 99% of all
: introductions lead to the extinction of the introduced species, as the
: become outcompeted by the local species, who have the advantage of
: 'home court'.
:
: In nearly all the remaining cases, the newly introduced species
: becomes a part of the ecosystem without causing a big upset.
:
: However, in some cases a new arrival will replace a local species,
: marginalizing it or driving it into extinction. It does happen. It has
: happened.
: That it doesn't happen *often* isn't really a defence.
:

[Elaine T]

perrin wrote:
> Or the new species will find an equilibrium with the existing species,
> within the eco-system. That seems to have been the case with the walking
> catfish, also released in the States. It was feared for its voracious
> appetite, hardiness, ability to walk onland (and spread) and reproduce
> quickly. It seems now that the hysteria was due to a basic misunderstanding
> of what the fish is - how much of a predator was it?
>
> My point is this, Mike - I'd like to understand how the eco-system copes
> with the new fish. I'm not saying that the dreaded scenario of replacement
> won't happen but I'd like to understand what happens in the majority of
> situation when the new fish is contained.
>
> Btw, any more info on snakeheads - reproduction?
>
> cheers
> perrin
>

Try google searching. That's all I usually do to start finding
information. As for how the new species interacts with the current
ecosystem, I'd rather not have the releases happen in the first place to
find out the hard way. There are plenty of existing examples to study.
Look at European starlings in the US. Those damn birds are
everywhere. With snakeheads, people are clearly too dumb to keep large
predatory fish out of waterways, so I am still in favour of the legislation.

--
__ Elaine T __
><__'> http://eethomp.com/fish.html <'__><
rec.aquaria.* FAQ http://faq.thekrib.com

[Mean_Chlorine]

Thusly Elaine T > Spake Unto All:

> Look at European starlings in the US. Those damn birds are
>everywhere.

Unlike in Europe, where they've declined sharply due to persecution.

[Mean_Chlorine]

Thusly "perrin" > Spake Unto All:

>Or the new species will find an equilibrium with the existing species,
>within the eco-system. That seems to have been the case with the walking
>catfish, also released in the States. It was feared for its voracious
>appetite, hardiness, ability to walk onland (and spread) and reproduce
>quickly. It seems now that the hysteria was due to a basic misunderstanding
>of what the fish is - how much of a predator was it?

To an Okeefenokee pygmy sunfish - plenty.

>My point is this, Mike - I'd like to understand how the eco-system copes
>with the new fish. I'm not saying that the dreaded scenario of replacement
>won't happen but I'd like to understand what happens in the majority of
>situation when the new fish is contained.

It's almost impossible to predict the outcome of an introduction
before it's done. Who'd have known before releaseing nile perch into
Lake Victoria that it'd lead to the extinguishing of perhaps 300
species of fish?

>Btw, any more info on snakeheads - reproduction?

What are you asking?

The reason it is opposed isn't because it is known it would extinguish
other species, but that noone knows what'll happen when it spreads,
and its introduction into the US gives no advantage. Sometimes
introduction gives big advantages, like introducing Salvinia beetles
did - southern USA have big problems with the introduced plant
Salvinia, and after *extensive trials* decided to release a predator
of Salvinia, but that's not the case with northern snakehead. The
snakehead WILL compete with indigenous predators like gar, bass and
bullhead, and WILL feed on indigenous fish, and noone wants a repeat
of what happened after the introduction of the sea lamprey into the
great lakes. Even if that may not be what happens. It could instead be
like when european brown trout was introduced - it did displace local
species, but does now support an important fishery.

But noone knows. The thing is, the risk of finding out is considered
unacceptable for the very small gain.

>perrin

[perrin]

I know the supposed risks, I'm not debating them...you misunderstand...my
question is, has anyone done any studies to see when the eco-system (and its
inhabitants) can co-opt the newcomer, and when the latter will overturn the
system??

"Mean_Chlorine" > wrote in message
...
: Thusly "perrin" > Spake Unto All:
:
: >Or the new species will find an equilibrium with the existing species,
: >within the eco-system. That seems to have been the case with the walking
: >catfish, also released in the States. It was feared for its voracious
: >appetite, hardiness, ability to walk onland (and spread) and reproduce
: >quickly. It seems now that the hysteria was due to a basic
misunderstanding
: >of what the fish is - how much of a predator was it?
:
: To an Okeefenokee pygmy sunfish - plenty.
:
: >My point is this, Mike - I'd like to understand how the eco-system copes
: >with the new fish. I'm not saying that the dreaded scenario of
replacement
: >won't happen but I'd like to understand what happens in the majority of
: >situation when the new fish is contained.
:
: It's almost impossible to predict the outcome of an introduction
: before it's done. Who'd have known before releaseing nile perch into
: Lake Victoria that it'd lead to the extinguishing of perhaps 300
: species of fish?
:
: >Btw, any more info on snakeheads - reproduction?
:
: What are you asking?
:
: The reason it is opposed isn't because it is known it would extinguish
: other species, but that noone knows what'll happen when it spreads,
: and its introduction into the US gives no advantage. Sometimes
: introduction gives big advantages, like introducing Salvinia beetles
: did - southern USA have big problems with the introduced plant
: Salvinia, and after *extensive trials* decided to release a predator
: of Salvinia, but that's not the case with northern snakehead. The
: snakehead WILL compete with indigenous predators like gar, bass and
: bullhead, and WILL feed on indigenous fish, and noone wants a repeat
: of what happened after the introduction of the sea lamprey into the
: great lakes. Even if that may not be what happens. It could instead be
: like when european brown trout was introduced - it did displace local
: species, but does now support an important fishery.
:
: But noone knows. The thing is, the risk of finding out is considered
: unacceptable for the very small gain.
:
: >perrin
:

[Mean_Chlorine]

Thusly "perrin" > Spake Unto All:

>I know the supposed risks, I'm not debating them...you misunderstand...my
>question is, has anyone done any studies to see when the eco-system (and its
>inhabitants) can co-opt the newcomer, and when the latter will overturn the
>system??

Yes, there are plenty of studies when species are intentionally
introduced (see e.g.
http://www.cips.msu.edu/ncr125/StateRpts2004MILab.htm ). The thing is
that there are so many unknown variables that it's hardly ever
possible to predict with anything resembling certainty, and for most
of the species released by hobbyists there is no appraisal of risks at
all*.
The restrictivity is based on the fact that sometimes introductions go
really horribly wrong - like Caulerpa in the mediterranean, fire ants
in Texas, rabbits and foxes in australia etc etc - so the default is
to stop all introduced species before they spread.

One must remember that an introduction if successful means extending
the range of one species, but if things go badly, may lead to the
total extinction of other species. That is, the risks nearly always
outweigh the benefits.

* Australia is an exception. Their bad experiences with previous
introductions has led them to now appraise risks of any imported
species, and ban species with a capacity to become established.

[perrin]

Thanks, will take a look at the site.

"Mean_Chlorine" > wrote in message
...
: Thusly "perrin" > Spake Unto All:
:
: >I know the supposed risks, I'm not debating them...you misunderstand...my
: >question is, has anyone done any studies to see when the eco-system (and
its
: >inhabitants) can co-opt the newcomer, and when the latter will overturn
the
: >system??
:
: Yes, there are plenty of studies when species are intentionally
: introduced (see e.g.
: http://www.cips.msu.edu/ncr125/StateRpts2004MILab.htm ). The thing is
: that there are so many unknown variables that it's hardly ever
: possible to predict with anything resembling certainty, and for most
: of the species released by hobbyists there is no appraisal of risks at
: all*.
: The restrictivity is based on the fact that sometimes introductions go
: really horribly wrong - like Caulerpa in the mediterranean, fire ants
: in Texas, rabbits and foxes in australia etc etc - so the default is
: to stop all introduced species before they spread.
:
: One must remember that an introduction if successful means extending
: the range of one species, but if things go badly, may lead to the
: total extinction of other species. That is, the risks nearly always
: outweigh the benefits.
:
: * Australia is an exception. Their bad experiences with previous
: introductions has led them to now appraise risks of any imported
: species, and ban species with a capacity to become established.
:

[Keith]

Check out http://www.invasivespecies.gov/ . They have plenty of
information on invasives, their impact, how they were introduced, etc.


There are a lot of scientific papers also available. If you search
Science magazine, for example, for "invasive species", you get
6,841matches. Nature yeilds 42,651!

So yes, there are bunch of people who study invasive species. They are
extemely important because of the devastating affects they can have on
the environment.

Keith

[winddancir]

Another example is predatory pike were released by an unknown person into a California lake. I can't remember which one. But there have been drastic measures taken to get rid of these fish and keep them out of the rivers. The authorities have poisoned, blasted, dreged, anything... but the pike keep coming back. Officials thought they had killed off the population of pike, but a year later they were back. It was suspected that some one released more into the lake. The pike in the lake have killed off most of the native fish, and are a menace in this situation.
Another invasive thing is a plant. Water hyacynth in the Sacramento or American river Delta. It has overgrown everything. It's a pretty plant and all, but it has grown soooo much that mats of it cover the entire water surface in most places. They have tried just scooping it off, and that doesn't really work. Poison was used for a while, and was kinda working, but then there was worry about what the poison was doing to the water. Now, they're thinking about using the poison again, because all the other methods they've been using haven't made any difference, other than the water hyacynth spreading even more. The plants have gotten so bad that boaters can't get through the stuff.

[Keith]

I just got my Discover magazine yesterday. The cover article is on
invasive species - and exactly how harmful they really are! I haven't
had a chance to read it yet, but it looks very interesting.

It should be on newstands or look for it online at www.discover.com
probably in May.

Keith