Photo courtesy of Nonindigenous
Aquatic Species Program
Don't Release Exotic Fish
Any plant or animal that is not native to the United States is considered
an exotic species. Most fishes available for sale in pet shops are exotic
and are imported predominantly from Central and South America, Africa,
and southeast Asia. Each year, over 2000 species, representing nearly
150 million exotic freshwater and marine fishes, are imported into the
United States for use in the aquarium trade. Fish culture in Florida
also results in millions of exotic fish available for sale in the industry.
If you have caught or seen any species that are not native to your area,
please let me know by using the Exotic
fish form. I will also add your sightings and comments
to the bottom of the page.
Unfortunately, a number of exotic fishes are released into the wild
each year. Hobbyists may not be able to take their fish with them when
they move, or they simply may lose interest in maintaining an aquarium.
Fish may also be released if they outgrow the aquarium or if they appear
to be in poor health. Whatever the reason, releasing exotic fish into
local waters is not a good idea. For one thing, it may be illegal. But
there are sound biological reasons, too:
- Released fish will be physiologically stressed upon introduction
to a different environment.
- They will be susceptible to parasites and diseases.
- They might be attacked by native predators, such as larger fish,
fish-eating birds, or water snakes.
It Isn't Good for the Environment
- If exotic fish survive and reproduce, they are difficult, if not
impossible to control or eradicate.
- They may cause changes in the existing aquatic community through
competition with native species or predation on them, as well as through
overcrowding or aggressive behavior.
- They may infect native fish with exotic parasites or diseases.
- An exotic may also affect the genetics of native species by hybridizing
- Some species may pose a physical or public health threat, such
as piranhas and freshwater stingrays.
Current Problems Currently, at least 126 different
species of exotic fishes have been caught in open waters of the United
States, and 46 of these are known to have established breeding populations.
Over half of these introductions are due to the release or escape of
aquarium fishes. Because many of these fishes are native to tropical
regions of the world, their thermal requirements usually prevent them
from surviving in temperate areas. In the U.S., therefore, most introduced
fishes have become established in Florida, Texas, and the Southwest.
Examples include a number of cichlid, such as the Oscar, Jack Dempsey,
jewelfish, convict cichlid, Midas cichlid, and spotted tilapia; and
livebearers, such as swordtails, platies and mollies, and armored catfishes.
The goldfish, a native of China, is one of the few examples of a temperate
aquarium species that is established throughout the U.S.
Alternatives to Release Instead of subjecting the
fish to potentially harmful environmental conditions or risking potential
ecological problems by releasing it, there are alternative means for
disposing of unwanted pet fish:
- Return it to a local pet shop for resale or trade.
- Give it to another hobbyist, an aquarium in a professional office,
a museum, or to a public aquarium or zoological park.
- Donate it to a public institution, such as a school, nursing home,
hospital, or prison.
If these options are not available, a veterinarian or fishery biologist
can euthanize it (put it to sleep) with anesthetic. You can also do this
at home by placing the fish in a container of water and putting it into
the freezer. Because cold temperature is a natural anesthetic to tropical
fishes, this is considered a very humane method of euthanasia. A pet shop
also may be able to assist you if euthanasia is the option you choose.
An excellent discussion of fish euthanasia was published in the September
1988 issue of Tropical Fish Hobbyist. This magazine is available through
pet shops or at your local library.
If you must give up your pet fish, please consider its well-being
and its potential impact on the environment. Do not release it into
a natural body of water.
Your comments on the alternatives:
I have a very humane alternative to euthanize your fish, if
that unfortunate event is necessary.
Buy pure clove oil. You can get it at a health food store for under $10
for a Ĺ ounce bottle. Put the fish in a medium sized mixing bowl in his
own water from his tank. In a small jar or something with a lid (I use
a cleaned out jelly jar) mix the clove oil with tank water. Put the lid
on and shake it like crazy over and over until the liquid in it is
white. Then pour a little into the mixing bowl with the fish. Swirl it with
your hand. The fish might fight it just a little bit and then slow
down. Then pour a little more in and swirl again. He should just go to
sleep and appear dead. If he doesn't, try a little more of the clove
solution, always shaking very well before an addition to the bowl. When he
goes to sleep, leave him in the solution for a good 10 minutes and then
put him in a small cup or zip-lock baggie and put him in the freezer.
Pain free death. Very humane. We should all go so easily.
This is a rebuttal to Lee's rebuttal. Who knows what fish "feel"?
Less than half a century ago doctors believed babies didn't feel
pain and would do surgery on them without anesthesia. Now they
know otherwise and even a routine circumcision is done with some
sort of topical anesthesia. Most people today would say "duh!"
and be horrified at doctor's past ignorance. Please don't say,
PhD or no, that you KNOW what fish feel. Both logic and common
sense, would indicate that anything with a nervous system feels
some sort of pain and discomfort. And higher, more complicated
animals, like mammals, birds, fish, perhaps even reptiles, are
capable of feeling great distress and pain. To assume otherwise
is just silly. We don't know what animals feel, we often don't
even know what each other feels. Pain is subjective (not relative,
but subjective). Pain is very real, and distressing to anything
'wired' (i.e. a nervous system) to perceive it. Thus, I think
it's safe to say that freezing a fish is likely to be as uncomfortable
and painful as boiling a lobster (ever hear the high pitched scream
they emit?). Let's not rationalize our actions with inaccuracies.
Re: freezing as a form of fish euthanasia, just say, "of course
it's likely to be painful, but we haven't come up with a better
solution yet." And from there, we can find a compassionate and
wise (not releasing them into the wild) solution. Both are important.
This is a rebuttal to the first comment placed on this website.
I honestly believe you are a caring person, but your science is
inaccurate. I am a fish biologist, and let me start of by saying
that Chris is being anthropomorphic by saying that the fish endures
pain by jagged frozen blood cells ripping through veins. No one
knows what the fish is feeling. Actually the cold reduces the
fishís core temperature, slowing down the heart to a stop, itís
not as if the blood freezes into jagged projectiles ripping through
veins at high speeds. In research we commonly euthanize fish in
this manner, other methods include using a sufficient dose of
MS-222, or the less commonly used pithing of the fish with a sharp
needle to the brain. There is no magic on/off switch for a fish.
Having an exotic species of pet is a responsibility everyone should
take seriously. You need to ask yourself, if you love your fish
why do you want to get rid of it in the first place, and also
do you realize by saving your one fish by releasing it into the
wild actually threatens many native species, you may be killing
more fish in the future then you could dream of. Also, Chris your
last sentence is hypocritical; you stated: Whether you chose to
believe this or take this suggestion off your site is up to you,
but I would personally rather release a fish than freeze it, and
I don't believe in releasing exotic fishes either. O.K. you would
rather release a fish than freeze it, but you donít believe in
releasing exotic fishes, so what would you rather do than releasing
it? As far as I know it is not illegal to release native fishes
in their native habitats.
I've studied a lot about fish since I first got into fish keeping
and I read something on your site I simply must make a comment
about. You talk about saving the environment, and being humane
while doing it yet when you mention fish euthanasia you say putting
a fish in a freezer is a humane form of it. This is not true,
cold temperature is not an "anesthetic" to tropical fishes. Tropical
fish slow down because they get their body temperature from surrounding
water so the cold makes them slow, so in a sense this could be
considered an anesthetic of sorts, but not truly. While the fish
appears to just "slow down and go to sleep" it is actually in
a great deal of pain. The cold itself is very painful to the fish
and when the actual freezing of the water starts the fish is still
alive and conscious enough to feel the pain. As the fish freezes
its blood cells freeze in jagged spiky balls ripping through the
veins, organs, etc. Whether you chose to believe this or take
this suggestion off your site is up to you, but I would personally
rather release a fish than freeze it, and I don't believe in releasing
exotic fishes either.
Your sightings and comments:
Fish sighted: Texas cichlid
Location: Hidalgo County Irrigation Canal, TX.
Fish sighted: Oscars, other cichlids, Asian catfish
Location: Florida, Big Cypress National Preserve L-28
In Florida, seeing exotics
is a normal occurrence. I have been fishing for native sunfish, and
then catch Mayan Cichlids (released in 1983), Jaguar Guapotes (released
in 1995), Oscars(not sure of release date), and countless Asian catfish.
I believe that it is despicable that people release these fish. Mayans
are proven to scare away largemouth, and tilapia overwhelm the Everglades.
So if you have a fish that you do not want, PLEASE, give it away or
euthanize it humanely. Do it for the natives!
Fish sighted: Oscar, Plecos, Peacock Bass, Tilapia
Location: Texas, San Antonio River
San Antonio River. Brackenridge Park near the SA Zoo.
Numerous exotics I have caught using a cast net including huge plecos, Oscars,
Pacus, Peacock Bass, Mozambique tilapias, and even a 20''+ Koi.
The waters of the SA river run right through the zoo, which could
explain the tilapias and such because the zoo has them all over the place in
their waters to eat hippo dung and such. I never but fish for my 7000
gallon pond I built. I just go to the park with a cast net, throw some
bread in the water and wait a couple minutes and throw my net. Then I
transport them to my pond. Several beautiful Koi are now in my pond well
over 20''!!! I have all the fish named above in my homemade pond.
Fish sighted: Clown knife fish, butterfly peacock bass
Location: Florida, West Palm beach
While fishing with my
dad on November 24,2006 at 4:30 we were fishing some rip rap for largemouth
bass when something hit my dads bait and he told my to get the net because
it was a big one when I went to net it it was a clown knife fish and
it wouldn't even fit in our net it was 28 inches long and weighted 10.5
pounds on digital scales and just 15 minutes later I caught a butterfly
peacock bass on a crankbait it was 15 inches long and weighted 2.7 pounds
both fish were caught on bomber Fat A crankbaits in firetiger and shad
From: Tim Shelton
Fish sighted: Oscar
Location: North Carolina, Local pond
Caught 12" Red Oscar while fishing for largemouth bass in a
local pond in Hendersonville,NC using a 2" salt impregnated tube style
Fish sighted: oscar
Location: Lake Woodlands, north of Houston TX
My cousin and his friend
where fishing in a man made lake in The Woodlands, 35 miles north of
Houston. His friend caught what appeared to be an Oscar-hybrid. It was
about 8 inches long and looked like an Oscar but had a forked tail.
He put it in his aquarium with another Oscar he already had. It lived
quite sometime. I've also seen mollies, goldfish, various African and
south American cichlids and gouramies in other man-made lake in The
Woodlands. Seems like a lot of people there are releasing unwanted fish.
From: Robert Boland
Fish sighted: Oscar
Location: Fort Gordon, Georgia
I was bass fishing on Fort Gordon, Georgia
at my favorite lake. At first glance, I thought a bluegill was following
my large bass lure. At second glance, I could see this was no fish I
had ever seen before! I tied on a small jig, and caught him. One of
my friends identified him as an Oscar, for he has a few at home himself.
Because I caught the fish right next to the dam (a road is on the dam)
I can only assume he got too big for someone's tank.
Fish sighted: Cichlids
Location: Florida, Everglades
You name it, they are here. Oscars were big
for a while but have now been eaten almost clean out of the habitat
by the Uropthalmus. I have caught Tilapia Mariae, walking cats, Port
cichlids, etc.... Its the Uropthalmus that's the worst. I stopped and
saw some the other day. In a single 10' x 10' area, one foot deep, there
were 40 breeding pairs with spawns. I never thought they would tolerate
each other that close. The nests were literally a foot apart. And this
was in a canal off of rte 41 in the middle of the everglades. There
were likely tens of thousands of them within a quarter mile of me. A
From: Loring Chien
Fish sighted: Goldfish
I was somewhat surprised and have now seen
this TV commercial several times. I'm referring to a Blue Cross, Blue
Shield of Texas ad shown in Houston and I'm sure some other places in
Texas. The gist of the commercial is a boy wanting to set something
free and ends up in the last frames showing the boy emptying a goldfish
bowl with goldfish into a natural pond or lake. This struck me as a
very bad image to be showing on TV as other children might try to emulate
this on their own with god knows what fish they find at home. I guess
the bad things are one, showing the act and two, glorifying it as something
desirable to do. Couldn't find an e-mail address on the blue cross site
that I could sent to without an health account.
Fish sighted: oscars, cichlids, pleco
Location: Florida, Various drainage canals, Miami area
Hello, I used to live in the Miami area for
several years and caught at least 3 species of cichlids along with oscars
while fishing for native gamefish on rod and reel. Also, have used small
cichlids (less than the size of my hand) for bait to capture quite a
few snook and tarpon in the drainage canals and other small interconnecting
lakes. Have also seen some truly monstrous (20 inches!) plecos living
on/in the many culvert pipes and headwalls constructed to carry the
water under the roads. I have also caught a couple of peacock bass that
were supposedly released by the Florida DNR to help control the exotics.
By the way, when fishing for crappies with 4# test, an oscar gives good
account of itself on rod and reel. The peacock bass is a great fighter,
also. Pound for pound I don't think they match a tarpon. Not much can.
From: Grace Hoffman
Fish sighted: Jack Dempsey
I have to write on people releasing exotic
fish in waterways. I brought my daughter last week to go fishing at
our local park and I happened to catch a jack dempsey there and he is
about 6 inches long. When I caught him I new immediately what kind of
fish it was so I grabbed my bucket out of the back of my car and now,
a week later the fish is still alive in my 55 gallon tank where it will
stay. It is stupid for people to release these fishes in the wild because
down here in Louisiana they will adapt real easy and eat all of our
native fishes. So by catching this fish I was able to explain to my
4 yr old by way of example that it is not good to let them go in the
wild, that it is better to bring it to the pet store. Click to see a
I received this email it applies to these fish: "badman"
I was surfing and came across your page. Critical
issue! I am a supporter of the NAS, an avid member of the American Cichlid
Association and the Texas Cichlid Association. Just a minor correction
to the above sighting. The fish pictured is a Cichlisoma (Herichthys)
cyanogattatum AKA Texas Cichlid. While I have not heard of one being
caught in LA, we have had many reported sightings of native populations
as far north as Austin. Likely this specimen was transported and released
or through some other form of contamination of the water supply. Just
thought you might want to accurately identify the Interloper.
Keith D. Pearson
Vice President Pearson Interests
O- (214) 522-7663
HERE FOR MORE SIGHTINGS AND COMMENTS
Information was graciously provided by the Nonindigenous Aquatic Species Program
and the U.S. Geological Survey. Please click on their logos for much more information.