- The Washington Times - Saturday, July 8, 2006

FORT BELVOIR — John Odenkirk knows snakeheads as well as anybody, but the invasive fish now living in tributaries of the Potomac River occasionally surprises him.

Mr. Odenkirk, a biologist with Virginia’s Department of Game and Inland Fisheries, is conducting a first-of-its-kind study, tracking the movements of 20 snakeheads tagged with radio transmitters.

Most of the fish have done what Mr. Odenkirk would expect — stay in the shallow, stagnant water of Dogue Creek, a Potomac tributary that has been the center of the snakehead invasion since they were discovered there in 2004.

But a few have moved. One swam across the Potomac, despite the species’ dislike of moving water, and settled in Piscataway Creek on the Maryland side of the river. But according to Mr. Odenkirk’s weekly tracking surveys, the fish has barely budged since making the long trek.

“He must have found something here he likes,” Mr. Odenkirk said, holding a loop antenna that helped him track the fish from a small motorboat.

The northern snakehead creates a commotion wherever it appears. Native to East Asia, it prompted a near panic in 2002 when thousands were found in a Crofton, Md., pond. Their ability to breathe air, survive on land, and adapt and thrive in foreign environments — not to mention their ugly appearance — inspired labels of “frankenfish” and even a B-level, made-for-cable-TV horror film, “Snakehead Terror.”

The fish in the Crofton pond were poisoned, but in 2004 more were found in Dogue Creek. Even greater numbers were discovered last year, prompting most fisheries biologists to acknowledge that snakeheads are here to stay. Snakeheads also have been found in tributaries of the Delaware River in Pennsylvania and a lake in the Queens borough of New York.

Steve Minkkinen, a project manager with the U.S. Fish and Wildlife Service who is developing a snakehead-management plan, said the goal in the Potomac should be control rather than eradication.

While snakeheads have proven their adaptability, the assumption has been that they would not tolerate the salinity of the tidal Potomac, preventing their spread into the Chesapeake.

But Mr. Minkkinen said more recent research shows snakeheads can tolerate salinity at levels similar to what is found at the mouth of the Potomac in certain times of the year.

Part of the problem is there has been little research on the snakehead, which could make Mr. Odenkirk’s work valuable.

So far, his research shows the fish fall into fairly predictable patterns. Most stayed in Dogue Creek and more than half of them are in roughly the same spot week after week.

Usually they seek shallow, stagnant water and cover from the sun.

Mr. Odenkirk uses an electrofisher that shoots voltage into the water that stuns most fish and forces them to float to the surface.

However, snakeheads dive violently to the bottom of the creek in a muddy splash when struck by a current.

“If you don’t get ‘em the first time, they’re gone,” Mr. Odenkirk said.

After a few tries, Mr. Odenkirk netted a big one — 7 pounds — in the exact spot he predicted he’d find the fish. As he held it up for examination, he pointed out the gullet, reminiscent of a prehistoric creature with rows of sharp teeth and a tonguelike protuberance.

Mr. Odenkirk says sharply curtailing the snakehead population will be difficult, but he thinks the best way will require knowing as much as possible about the life cycle, which is why he thinks the radio tracking is worthwhile. Last fall, the fish seemed to migrate en masse up Dogue Creek. If the radio tracking shows a similar migration this fall, biologists and anglers might be able to round up vast numbers of them.

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