The search is on for an exotic snakehead
Janesville, Wis. It’s a fish biologist’s worst nightmare: A
giant exotic predator fish, known for its voracious appetite and
its uncanny ability to breathe humid air and wriggle across
The northern snakehead first made news a few years ago when a
population was found in a pond in Maryland. News quickly spread
about the havoc such a fish could wreak on native fish populations.
Now, its much larger cousin, the giant snakehead (Channa
micropeltes), has somehow found its way into Wisconsin’s Rock
According to Don Bush, DNR fisheries biologist, the fish was
identified only after a team of DNR workers first captured the
24-inch long alien and then released it while conducting a fish
survey on the Rock River.
The giant snakehead, which is a native of Southeast Asia, was
initially misidentified as a bowfin and returned to the river after
the crew snapped a photo.
“There are 28 species of snakehead, and most are tropical and
wouldn’t be able to survive our northern winters,” said Bush, who
was on the team that captured the fish.
Bush said the individual fish they saw had reddish and purplish
markings on it, which they thought was unusual for a bowfin, but
not enough to raise red flags.
“We captured thousands of bowfin that day and we weren’t even
thinking it could have been a snakehead,” Bush said.
Fisheries biologists Dr. Walt Courtney of Florida Atlantic
University later identified the fish in the photo as a giant
snakehead and a second survey of the river where the fish was
netted failed to find that fish, or any other individuals.
“Dr. Courtney verified the identity of the fish, and he was
confident that it was a southern species and would not be able to
survive water temperatures in the winter,” Bush said.
Most people believe the fish was likely a pet that was released
into the river illegally.
“People like having strange and exotic pets,” Bush said. “It
probably got too big and someone released it.”
According to Bush, DNR fisheries managers executed several fish
sampling operations of the Rock River between Janesville and Beloit
to determine if any more snakeheads are present, but none were
found. The fish caught in the DNR survey is the only one known to
have been found, and the DNR is hoping it will not survive the
winter. Bush is somewhat suspicious, however, that the fish might
have been in the river longer that originally thought. He said that
because of the size of the fish, and the location in which it was
found, it may be possible that it has been in the Rock River for
much longer, and found a way to over-winter in warm-water
discharges from a nearby power plant.
“Our crews have finished (sampling) and we were not successful
in catching any snakeheads,” Bush said after crews attempted to
relocate the fish. “We will probably go back into the heated
effluent from the power plant this winter to see if we can find
The giant snakehead is a large, aggressive freshwater fish that
can grow up to 36 inches. The DNR wants to see it banned from the
aquarium fish trade. According to the DNR web site, adult
snakeheads need a large tank that can hold at least 150 gallons of
water and they can quickly outgrow the average home aquarium, which
could possibly result in owners getting rid of them by releasing
the fish into the waters of Wisconsin.
“It is clear that Wisconsin must follow the lead of other Great
Lakes states, including Illinois, Indiana, Michigan, Minnesota, and
Ohio, and ban the possession and trade of live snakehead fish,”
said Mike Staggs, DNR Bureau of Fish Management director.
Bush said that at this point it appears to be an isolated
incident and there is no evidence to suggest that there is a
breeding population in the Rock River.
Releasing aquarium fish to the wild is illegal in Wisconsin and
can result in exotic species becoming established, much to the
detriment of native fish.
According to Bush, all species of snakehead fall under the U.S.
Fish and Wildlife Service’s Lacey Act, meaning the federal
government bans importing or transporting all snakehead species
between the continental U.S., the District of Columbia, Hawaii and
Puerto Rico. The federal ban doesn’t make it illegal to own or
possess a snakehead where they are allowed, but it does bar their
transfer between states or importation into a state.
Bush said that while snakehead is very similar in appearance to
the native bowfin, the distinctive differences include pelvic fins
being located directly underneath the pectoral fins and the
distinct reddish color not typical of a bowfin.