Re: NANFA-- Introduced fish

Bob Bock (
Sun, 31 Mar 2002 15:04:09 -0500

Since we're on the subject of introduced species, here's an article I wrote
on the topic some years ago, copied from the NANFA Web site:

The North American Native Fishes Association

What to do About Introduced Species?
by Robert Bock

Maryland longears. West Virginia guppies. Florida cichlids. Colorado River
angelfish. Michigan sea lampreys. And everywhere-- bluegills. We human
beings have an incredible propensity for moving other species around.
According to the Office of Technology Assessment's 1993 report, Harmful
Non-Indigenous Species in the United States, at least 4,500 species of
foreign organisms have established free-living populations in the United
States. These include not only plants and plant parasites, but also insects
and other invertebrates, birds, mammals, and at least 126 species of fishes,
47 of which are known to have established stable breeding populations.

Presumably, the list does not include species native to one part of the U.S.
and established in another. If you're new to NANFA, you may not realize that
fish native to this continent can often do as much damage once they're
transplanted to another drainage system as any species from a foreign
country could. Sometimes people introduce species deliberately. Rainbow
trout, striped bass, and large and smallmouth bass have been introduced far
outside their original ranges to establish both recreational and commercial
fisheries. The Great Lakes salmon fishery is based on the coho salmon, a
species native to the West Coast. Other times, new species arrive by
accident. An unintentional stowaway, a European perch called the ruffe, was
taken on in the ballast tanks of ships headed to the U. S., and escaped when
the ships discharged their ballast water in the Great Lakes. (Dan Logan
speculates that an Asian shrimp he and the other Northwest NANFA members
discovered in Oregon was introduced to the U.S. this way.) Similarly, fish
raised for the aquarium trade and sport fishing may escape in the hatchery

At still other times, new species become established through various
combinations of kindheartedness and indifference, when people release pets
they no longer wish to keep. Goldfish, an Asian native, now live in ponds,
lakes, streams, and rivers throughout the U.S. In the Winter 1996 issue of
this publication, the Riffles column contained an item about freshwater
angelfish that were thriving in a weedy stretch of the Colorado River.

The warm waters of Florida, Texas, and other parts of the Southwest have
become a haven for free-living populations of oscars, Jack Dempseys,
jewelfish, firemouths, convicts, midas cichlids, tilapia, swordtails,
mollies, platies, croaking gourami, walking catfish, and at least three
species of suckermouth (loricarid) cats. And a few years ago, when I visited
the thermal springs in Berkely Springs, West Virginia, I was surprised to
find veil-tall guppies thriving and reproducing in the warm water!

These introductions can be disastrous. Roughly $10 million is spent each
year on research and control of the parasitic sea lamprey, which migrated
from Lake Ontario to the other Great Lakes when the Welland Canal was
constructed. We notice the effects of introductions when they exact a heavy
financial toll. But if an introduction doesn't affect us economically, we
probably aren't going to pay much attention to it. Few people will care if
stocking rainbow trout in a midwestern stream reduces the populations of
native darters and sculpins that hardly anyone knew were there in the first

And the damage such introductions do may not become apparent for many years.
When I was a kid, my family and I would visit my uncle in the Catskills and
I would fish in the lake nearby. Occasionally, I'd pull in a golden shiner
among the yellow perch and pumpkinseed sunfish that were unlucky enough to
try to eat the worm at the end of my bobber. The shiners were introduced
into the lake by fisherman who dumped the contents of their bait buckets
into the water when they were through fishing. When I visited the lake again
about 25 years later, the native perch and pumpkinseeds appeared to have
been severely out competed by the shiners. I pulled in about 50 shiners that
morning and only a few pumpkinseeds and perch.

And who knows what effect such an introduction will have on the local
species in 25 more years? I fear that in many cases, the damage we do may
not become apparent until long after we're gone. Who can say whether
smallmouth bass stocked in a northeastern river today won't lead to local
extinctions 50, 100, or even 1,000 years later?

Sometimes introductions have consequences no one could have predicted. For
example, the seemingly innocent stocking of one fish in Arkansas seriously
jeopardized an endangered species in Utah. In 1968, the Arkansas Game and
Fish Commission introduced the Asian grass carp into Arkansas lakes. The
fish soon spread to the Mississippi River and became established. The grass
carp carried with it from Asia a parasitic tapeworm that eventually spread
to red shiners, a popular bait fish. Anglers or bait dealers introduced the
infested shiners into the Colorado River, and by 1984 the shiners had found
their way to the Virgin River in Utah. Here the tapeworm infected the
woundfin, a native minnow already endangered because of dams and water
diversions. Not as resistant to the tapeworm as were the red shiners,
perhaps weakened due to competition with the shiners for food and space, the
woundfin suffered a rapid decline from which it has barely recovered.

To complicate matters even more, human beings have also gained the ability
to create new "species" where none existed before. Last spring, I was trying
to catch some pumpkinseed sunfish for my 65 gallon aquarium. In recent
years, this native species has become hard to find in my part of Maryland.
After hooking and releasing a dozen of the introduced bluegills, I reeled in
what I thought was the most colorful pumpkinseed I'd ever seen. On close
inspection, however, this fish had a much larger mouth than a pumpkinseed,
and a pale orange trim around the edges of the fins. I've tentatively
identified it as a cross between a pumpkinseed and a green sunfish. How it
got there, I have no idea, as there aren't any green sunfish around for

Hybrids like this one, though, are often stocked, as it's assumed they won't
reproduce. But in a recent posting on the NANFA E-mail list, Garold W.
Sneegas reported that a small percentage of bluegill x green sunfish hybrids
that were stocked in a Kansas pond had indeed reproduced. Such hybrids often
grow larger and are more tenacious than either parent species--stiff
competition for the native fish that are forced to share their environment
with them. And we can only expect the competition from man-made hybrids to
get worse, as genetic engineers tamper with the genes of existing species to
create fish ever more suited to sportfishing.

To be sure, the Genie's already out of the bottle and there's no chance of
returning things to the way they were before Europeans came to this
continent. Once a species becomes established, it's difficult to eradicate.
And as much as I hate to admit it, to a certain extent we depend on exotics.
Sportfishing is a multi-billion dollar industry. If we could eliminate all
introduced species tomorrow, people who make a living on everything from
worm farms, to bait shops, to lure manufacturing, to angling magazines would
be thrown out of work. But as the number of native fish enthusiasts grow,
we'll be in more and more of a position to influence things, by lobbying
State legislatures and natural resource departments and letting them know
when their plans to introduce new species are a bad idea. Perhaps we can
even be influential in the creation and maintenance of "sanctuary
districts"--streams, lakes, and ponds where exotics would be prohibited and
natives could flourish.

But until the time comes when NANFA becomes a big, powerful organization,
there's still a lot we can do. First, there's the matter of personal
responsibility. In big, bold, capital letters, so you never, ever forget:
Even if the fish doesn't find another of its kind to reproduce with, it
could still spread diseases or parasites. Similarly, if you're going to keep
fish from a number of different places together in the same tank, you
shouldn't release them back into the wild. If you can't keep them or find a
good home for them, it's better to euthanize them.

You should also be careful not to transport water from one system to
another. Your flooded waders or seemingly empty bait bucket might contain
unseen parasites or larvae that could have a damaging effect in new waters.

As NANFA members, we can also encourage the removal of non-natives from the
environment. Peter J. Unmack regularly leads trips to the Nevada desert to
remove largemouth bass and other introduced species from desert springs,
where they pose a serious threat to the native spring fish.

We can also encourage the collection of introduced species that make
interesting aquarium fish. I'll start: In this issue, we're publishing
information on where to collect the longear sunfish from the C&O Canal in
Montgomery County, Maryland. I haven't been able to identify the particular
longear subspecies I found while angling there last year. Even though it's
not as colorful as the one in Robert Rice's Tropical Fish Hobbyist article
on the subject, it's still a nice little aquarium fish. We've published a
map and other practical information, so if you're ever in the area, you can
try your luck. Most aquarists dream of collecting in the Amazon or in
Africa. In fact, they don't have to travel so far.

Cichlids and other exotics are established in Florida and many other places
in the South. Again, NANFA members can help by encouraging people to get
these exotics out of the environment, either to collect them for home use,
or for distribution to pet shops. I'm also asking our Southern members to
get together and pool their knowledge, to write an article like "Amazon
collecting in Florida," or "Cichlid collection in the South." (I'd write it
myself, but I'm unfamiliar with the locale.) I envision the article as a
practical, how-to guide, complete with maps and such useful information as
where to write for permits. The best place to submit it would be Tropica1
Fish Hobbyist. We could reach a lot of tropical keepers who've never
collected before, and get them out into the ponds and streams. At the end of
the article, you could mention NANFA and natives, and get them used to the
idea that there are interesting natives, as well. If you pulled this off,
you'd get a by line, a check, and a chance to publicize NANFA and perhaps
net us a few more members. If you'd like some editing help before you send
the article off, Chris Scharpf and I would be glad to help. For more
information, check out the Nonindigenous Aquatic Species (NAS) Information
Resources web page at .

Used with permission. Article copyright retained by author.

----- Original Message -----
From: "Gordon James" <>
To: <>
Sent: Sunday, March 31, 2002 2:05 PM
Subject: NANFA-- Introduced fish

> Hi!
> I was looking around at info on introduced fish.
> Hawaii's introduced fish list (not official list) for fresh water looks
> most of my tropical tanks.
> below is a quote of text from page.
> Fresh Water Animals
> of
> Hawaii's Watersheds
> Introduced Fish:
> --------------------------------------------------------------------------

> ----
> Dojo loach
> Introduced prior to 1900 on Kaua'i, O'ahu and Mau'i. Used as bait.
> Adult size 4 inches (10 cm) in length.
> --------------------------------------------------------------------------
> ----
> Convict cichlid
> --------------------------------------------------------------------------
> ----
> (Golden) Tilapia
> Introduced in the 1950's. Cultured for food in Africa and Asia.
> Characterized by the long dorsal fin. Differentiated from the bluegill by
> having no blue or black opercular flap. Useful to control aquatic plants
> irrigation systems and as a food fish. Adult size 4-6 inches (10-14 cm) in
> length. Young have, dorsally, horizontal black bars.
> --------------------------------------------------------------------------
> ----
> Family Poeciliidae:
> Swordtails, guppies, mollies and top minnows. Common in streams, ponds,
> resevoirs. A large family of small, live-bearing fish. Used as aquarium
> and as bait fish. Suitable for classroom aquariums. Mosquito fish are also
> member of this family.
> Mosquito fish
> Brought from Texas in 1905 for mosquito control. Abundant in lower reaches
> of streams. Can reach a length of 1 inch (2.5 cm).
> Swordtail
> Molly
> Guppy
> Family Loricariidae:
> Armoured catfish
> (Armoured catfish) variations
> /"Unless stated otherwise, comments made on this list do not necessarily
> / reflect the beliefs or goals of the North American Native Fishes
> / Association"
> / This is the discussion list of the North American Native Fishes
> / To subscribe, unsubscribe, or get help, send the word
> / subscribe, unsubscribe, or help in the body (not subject) of an email to
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> / For more information about NANFA, visit our web page,
/"Unless stated otherwise, comments made on this list do not necessarily
/ reflect the beliefs or goals of the North American Native Fishes
/ Association"
/ This is the discussion list of the North American Native Fishes Association
/ To subscribe, unsubscribe, or get help, send the word
/ subscribe, unsubscribe, or help in the body (not subject) of an email to
/ For a digest version, send the command to
/ instead.
/ For more information about NANFA, visit our web page,