Maryland taskforce to determine fate of infested pond.


Mar 11, 2001
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After Solving Snakehead Puzzle, Md. Moves In for the Kill

A northern snakehead fish normally found in China that was caught last month in Crofton, Md. (AP/File Photo)

By Anita Huslin, Washington Post Staff Writer

July 19, 2002

With the death sentence issued, the question now is: How best to execute a fish?

For the untold number of northern snakeheads -- the nonnative, air-breathing, slithering fish discovered last month in a Crofton pond -- it is safe to say that the end will not likely come by salt. Back-of-the-envelope calculations quickly revealed the impracticality of trucking the hundreds of tons that would be required to choke the fish to death. Chlorine was considered but rejected because it's too caustic to humans and the effects could linger.

Instead, experts on a task force convening in Annapolis today will offer a small, but more effective menu of options to Maryland officials who hope to rid the pond of the strange fish that can gobble up huge numbers of other fish and then wriggle on land to new waters.

They include antimycin A, a chemical that has been used elsewhere to control rampant carp populations, and explosives, which can blow the fish out of the water. And there's also the low-tech option of capturing the snakeheads with nets.

But a poison known as rotenone has been the hands-down favorite of fish experts facing similar dirty jobs. Derived from the ground-up leaves and roots of trees found in India and South America, it has been used since the 1940s as an agricultural pesticide and piscicide.

Paul Shafland, director of the nonnative fish research laboratory for the Florida Fish and Wildlife Conservation Commission, has faced dozens of species of invaders and has vanquished a half-dozen with rotenone.

"We have a standing policy of eliminating [alien] fish" in isolated locations, said Shafland, one of the task force experts. "Rotenone is the only fish toxin I use."

It works by blocking the transport of oxygen through the gills of the fish. Biologists dump it in the water and mix it around using the propeller of a motor boat, and within minutes, fish should start floating to the top.

"The water turns milky, the fish suffocate, and an air-breathing fish like the snakehead will come to the surface," said Walter Courtenay, a leading expert on invasive species who confirmed that the creatures were snakeheads. "If you've got enough people out there with dip nets, you can just capture these little guys on the spot."

Last week, state biologists caught 80 baby snakeheads in the weed-choked pond behind a shopping center. It was a disturbing sign that two snakeheads had spawned in the two years since they were dumped in the pond by a man who had originally intended to make soup of them. Since then, scientists have been experimenting with different kinds and concentrations of chemicals to determine the most effective way of exterminating them.

The use of rotenone has grown somewhat controversial in recent years after several cases in which the poison was used with unintended results. In one of those cases, California officials poisoned a public water supply while applying rotenone to Lake Davis, which had become overrun with nonnative pike.

About 30 years ago in Maryland, flies swarmed for miles over an inland beach on Assateague Island, where wildlife managers killed off thousands of fish in a failed attempt to test the effectiveness of rotenone against other techniques.

"It was a good idea, but the execution failed," said retired state biologist Nick Carter, who supervised the kill at Inlet Slough. Workers spent days cleaning dead fish off the beach, he recalled. "Everybody remembers it and laughs at me. It got pretty smelly."

Don Boesch, president of the University of Maryland Center for Environmental Science, who is chairing the snakehead task force, said he hopes to recommend a course of action for the state within a month.

End article


Florida's Dr. Snakehead is making a house call

Alien fish draws expert to Crofton pond in search of ways to kill its spawn

By Rona Kobell, Baltimore Sun Staff

July 19, 2002

GAINESVILLE, Fla. - Few people in this country know more about the sharp-toothed Asian fish that has invaded a Crofton pond than the man some here call Dr. Snakehead.

For the past year, Walter R. Courtenay Jr. has pored through reams of papers in a trailer in the Central Florida woods to assess the risk of the snakehead to native fish species.

Today, the 68-year-old ichthyologist will join a dozen other scientists on Maryland's recently formed snakehead panel to discuss how to get rid of the fish - known for its tendency to devour other species, move on land and survive out of water for several days. It's been multiplying feverishly in a pond behind a Dunkin Donuts along Route 3, and experts worry it could get into nearby waterways.

Though Crofton is the first place that a northern snakehead has been found to have spawned in this country, Courtenay believes it won't be the last.

"Can you imagine all the things we don't know about?" he asked in an interview in his lab this week. "That's the really scary part."

Concerned about snakehead sightings in a few spots around the country, the government brought Courtenay out of retirement last fall to work on the snakehead study at the U.S. Geological Survey's Florida Caribbean Science Center. The Florida Atlantic University professor emeritus returned to a familiar and collegial lab that he had visited many times in his 40-year career.

The lab is the sort of place where scientists wear fish shirts, display fish-inspired cartoons below fish nameplates on their doors (Courtenay's is a snakehead), and send ill co-workers fish-covered get-well cards. It's not the kind of place that usually fields calls from reporters or sees its research mentioned on late night comedy shows.

Courtenay, who owns about 70 fish shirts himself, doesn't mind the attention he and the snakeheads are getting. Nor do his colleagues.

"It's good for the issue. Unfortunately it takes some sort of exotic invasion to bring this home to people," said fishery biologist Amy Benson. "I wish we didn't have these jobs, but somebody's got to look into this stuff."

Experts say Courtenay is the right person for the job.

"In North America, he's about as good as it gets," said Robert G. Howells, a fishery research biologist with the Texas Parks and Wildlife Department who worked with Courtenay when snakeheads were discovered in Houston fish markets last year.

Courtenay, who is working with two other scientists, James Williams and Leo Nico, said the snakehead study is a first for the government. "Someone realized there was a small segment of the aquarium fish trade that was selling snakeheads and some of them had been turned loose by fish owners," Courtenay said.

The report is due next month.

Last year, Courtenay and his team began e-mailing others in the "fish net" - an informal group of biologists who trade information - to see what they knew. He already knew the snakehead could survive out of water for three days, walk on its fins, and eat voraciously. But he soon learned 25 species -such as bull's eye and northern - live from the Yangtze River in China to as far north as Siberia. Many Asian cultures ascribe healing powers to the fish. Folklore has it that snakehead oil is used to prevent scarring after C-section operations.

Because it is illegal to buy a snakehead in Florida, team members searched for snakeheads in Asian markets while on vacation in Missouri and New York where they are legal. They asked colleagues to keep their eyes peeled.

They bought a bull's eye snakehead online from Rhode Island. Buster, a northern snakehead, arrived from a colleague in Boston. Williams bought Ollie, another northern snakehead, from a fish market in Orlando. The salesman, who told Williams that Ollie was a "very special catfish," recently had a not-so-friendly visit from fisheries agents.

Courtenay concluded that the northern snakehead - the species found in Crofton - was the most dangerous because it can live from the tropics to Siberia.

"We're talking cold," he said. "That fish can live anywhere it wants to in the United States."

But that point was largely academic at the time: Even though one northern snakehead had been caught in a California reservoir in 1997, and two had been caught in the St. Johns River in Orlando in 2000, the fish generally could only be found in tanks in Asian markets.

Then in June, officials from the Maryland Department of Natural Rescources e-mailed a photo of a strange fish that had been caught in the Crofton pond. Courtenay immediately identified it as a northern snakehead, confirming the fish was nesting 75 yards from the Little Patuxent River.

Officials later determined that a local man had dumped two adult snakeheads-one male and one female - into the pond two years ago after they outgrew his aquarium. Earlier this month, DNR officials captured about 100 young snakeheads. Courtenay fears thousands are lurking - merchants typically sell snakeheads when they are about two years old and at their sexual peak. Do the math, he says, and it adds up to a third generation.

But, some scientists say Maryland's fish story has been blown out of proportion.

"These stories tend to get exaggerated and take on a life of their own," said Paul Shafland, director of the Florida Fish and Wildlife Conservation Commission's nonnative fish research lab in South Florida. "You hear the fish have teeth, they breathe air. Pretty soon you hear they climb trees, they eat dogs, they tap-dance, whatever."

Shafland, who is also on the Maryland panel, said the question of the snakehead's danger is one of perspective, and that native fish are far more resilient than some think.

But the Gainesville team says the Crofton discovery bolsters their conclusions - that snakeheads are dangerous and federal law should prohibit anyone from importing them alive.

"People said, what's the probability of them ever reproducing? Well, now we know. How would two fish in 10 acres of water find each other? Well, they did," Williams said. "I can't predict today that snakeheads are going to enter every stream in the Mississippi and wreak havoc on all fish populations, but it certainly has the potential to happen."

The snakehead saga reminds Courtenay of an old fish story.

In 1967, Courtenay had just begun what would be a 30-year career teaching zoology at Florida Atlantic University when the Asian walking catfish arrived in South Florida. The working story is that it escaped from a fish farm, where a man raised it because he thought its albino color would be popular with collectors. Later, the fish farmer's brother told Courtenay it jumped out of its tanks as he drove from Miami International Airport.

Either way, the predatory fish navigated the canal system like a beltway, chomping on every fish it met. Officials soon banned them in the state, prompting farmers in Tampa to dump their collections. Tampa's fish moved south while Miami's headed north, and by the time the species met in Lake Okeechobee, Courtenay said, little could be done for the native fish.

The walking catfish hooked Courtenay on invasive species, which he's studied ever since. It also taught him an important lesson about prevention. He keeps a walking catfish paperweight on his desk as a reminder.

Courtenay has worked tirelessly on the snakehead problem - his wife, Pat, sneaked a laptop into the hospital last weekend after he was rushed to the emergency room for digestive problems. He read e-mails and news reports as he recovered.

And while he expects some belly-aching from snakehead enthusiasts for recommending a ban, he said the government should seize the opportunity to keep the willful fish from spreading.

As if to drive the point home, Courtenay reaches into the bull's eye snakehead's tank. Immediately, the asphalt-colored fish sprouts spots resembling tire tracks - a fight-or-flight reaction. Williams lowers a net, but the fish jumps out twice, pirouetting back into the water. It digs its teeth into the netting until Courtenay pulls it out.

"Here's your snakehead," Williams said. "Now, as for where it's going to go, and what it's going to do..."

"It will determine that," Courtenay interrupted. "Not us."

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