Aug. 23 2004
Two bighead carp recently caught by an angler at Cherry Creek Reservoir
have raised a red flag for state aquatic biologists, who are concerned
the discovery could have serious, long-term implications for state
fisheries and recreation.
This is the first time we have seen this unwanted species in
any of our sportfishing waters in Colorado, said Pete Walker,
senior fish pathologist for the Colorado Division of Wildlife. "I'm
sure whoever released them did not understand the potential impacts,
but it's a terrible thing, and it's very much against the law to let
fish like this loose in state waters."
Walker identified the fish as bighead, a species of Asian carp that
eat large quantities of zooplankton. He and other aquatic experts
worry that, in sufficient numbers, bighead carp could negatively impact
sportfishing at impoundments around the state. Aquatic biologists
said zooplankton is the primary food source for young fish and adult
gizzard shad, the most important forage species for eastern Colorado
reservoirs. Fishery managers use shad as food for larger, more desirable
sportfish such as walleye.
Another serious and more immediate threat to humans is the bighead
carps reaction to motor boats. The fish, which can grow more
than 4 feet in length and weigh 100 pounds, tend to swim through surface
waters. When startled, they can jump up to six feet in the air, sometimes
right onto boat decks.
They actually have caused serious harm to peoplebroken
arms and legs, said Tina Proctor, aquatic nuisance species coordinator
for the U.S. Fish and Wildlife Service. We obviously are very
concerned for the safety of people as well as the effects they can
have on the native species.
State and federal biologists are concerned that bighead carp might
have spread downstream to the South Platte River, where river flow
could provide the habitat they need to successfully reproduce. Large
adult females can produce as many as 900,000 eggs per year, according
to research data.
Available evidence indicates that fish farmers imported bighead carp
to the southern United States in the early 1970s. Two other species,
grass and silver carps, also were imported into the country. In the
early 1980s the fish began to appear in public waters, the likely
result of escape from fish farms and aquaculture facilities. Bighead
carp have now been recorded in or along the borders of at least 18
states. More recently, another Asian species, the mollusk-eating black
carp, was imported into the U.S. Southeast.
Federal wildlife officials are concluding a three-year research project
to study the effects of bighead carp on native species in Colorado,
Montana, Wyoming, Utah, the Dakotas, Nebraska and Kansas. Results
are due to be released this fall, the U.S. Fish and Wildlife Service's
Proctor said there are many things people can do to prevent the spread
of bighead carp and other invasive species, including:
-- Learn to identify bighead and other large carp species;
-- dispose of unwanted live-bait fish in the trash, and not in the
water, because bait fish could contain unknown species;
-- never move live fish from one body of water to another;
-- drain lake or river water from a boats live well and bilge
before leaving a body of water;
-- and inspect and remove aquatic plants from boat water and trailer.
The bighead carp is characterized by its terminal mouth, located toward
the front of the head; a pronounced under-bite; small trout-type scales;
low- and forward-set eyes; and other distinguishing features.
The Bighead and Silver Carp Watchcard, a pocket-size card containing
identification and prevention information, is available from the Colorado
Division of Wildlife via e-mail at email@example.com or from
the USFWS via e-mail at firstname.lastname@example.org.
In addition to the bighead carp, two other exotic fish species have
been identified this month by Colorado wildlife biologists. A pacu,
a vegetarian relative of a piranha, and an arawana, a large top-level
predator species, were caught by anglers in the southeast Denver metropolitan
area. Both of these species are often kept as pets in tropical aquariums,
and owners sometimes release them when they get too large for tanks.
Colorado's Walker said people illegally release a number of exotic
fish species into Colorado waters each year, which could result in
far-reaching, long-term impacts on the state's $650 million-per-year
People think all the aquarium species are tropical and unable
to stand the cold weather in Colorado, but that is often not the case,"
Releasing fish and other aquatic wildlife into Colorado ponds, streams
and lakes is illegal without proper licenses and permits. State wildlife
officials ask anglers who catch exotic species to report them in person
(with fish in hand), or via phone or e-mail. Information can be sent
to the Colorado
Division of Wildlife, Aquatic Wildlife Section, 6060 Broadway,
Denver, CO 80216; by phone at 303-291-7362, or via e-mail to email@example.com.
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