Biologists test snakehead poison

The Washington Post

OXFORD, Md. - The end of the notorious, omnivorous, amphibious northern snakeheads began Tuesday in a state laboratory chamber marked QUARANTINE, a room where subjects arrive living but always leave dead.

Measured out carefully and diluted with well water, the poison came in a tray full of plastic bottles, each marked with the concentrations of toxin they contained: 1.5 parts per billion.

Their vigor and voracious predatory nature are what brought them to this end and prompted U.S. Secretary of the Interior Gale Norton Tuesday to brand them as "something from a bad horror movie," then propose a ban on their importation and interstate transportation. That ban could take effect in 60 days.

"The potential threat from release of the fish extends well beyond the local area and has national implications," Norton said, standing next to a foot-long specimen that had been preserved and stuffed. "We simply must do everything we can to prevent them from entering our waters, either accidentally or intentionally." Native to the Yangtze River region of China and capable of living through the coldest winters and hottest summers, the northern snakehead is a top-of-the-food-chain predator, biologists say.

In the case of the snakeheads discovered last month in a fishing hole behind a Crofton, Md., shopping center, investigators determined that two of the fish had been released by a well-meaning man who had planned to cook them but dumped them into the pond instead, unaware of the ecological consequences.

By dumb luck, the pair were male and female and proceeded to populate the pond. Now, 2 1/2 years later, officials fear there could be hundreds, if not thousands, of baby snakeheads grazing their way to adulthood and threatening to upset the natural order.

A task force of experts is preparing to recommend that the pond and everything in it be exterminated to eliminate the risk of the snakeheads escaping into the nearby Little Patuxent River.

With breathing apparatuses that allow them to gulp air, fins that enable them to slither along the ground and the ability to live out of water for days, the snakehead could wreak havoc on native fish populations, biologists say.

So with their death sentence certain, the question that remains is how much poison will be needed to kill all the snakeheads in the pond.

The answer, if not already evident, should come within days. University of Maryland biologists Andrew Lazur and John Jacobs Tuesday began the process of titrating the poison rotenone into bottles for use in the aquariums containing the baby snakeheads.

Used for more than half a century in the United States and derived from the ground-up leaves and roots of trees, rotenone works by blocking the fish's ability to filter oxygen from the water.

The experiment began at precisely 2 p.m., when Lazur and Jacobs placed a bottle of the rotenone solutions before each tank.

Eight bottles for eight tanks, each containing eight fish and a scrap of Styrofoam board, which the scientists placed there to see if the fish would try to slither onto them to escape the water.

One by one, the scientists dumped the bottles in, then turned up the aerators in the tank to stir in the solutions.

A chemical odor wafted through the cramped quarantine lab but was quickly diluted by the smell of the dank water in the tanks.

"I can't see anything," said Jacobs, peering into the murky water.

Within minutes,though, things starting moving. "I've got darting and gulping," said Lazur, inspecting a row of four tanks opposite Jacobs. "There's three on the beach." In the tanks with the highest concentration of poison, the three-inch baby snakeheads were darting rapidly through the water, diving and surfacing to escape the poison and gulp fresh air.

The experiment was designed to take three days but could be cut short if all the fish die before then.

An hour after the experiment began, biologists began counting the baby snakeheads that had rolled onto their sides and floated to the top. In the end, they say all of them will die, precursors to the main event in the pond.

"Someone thought they were doing those fish a favor" by releasing the fish into the pond, said Lazur, peeling off a pair of blue latex gloves. "It would've been more humane to just kill them."