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Parrot's Feather

A popular aquatic garden plant that spreads with water currents, animals, boats/trailers and fishing gear. Dense stands can stagnate water, and increase breeding grounds for mosquitoes learn more »

Zebra/Quagga Mussels

These tiny freshwater mussels clog drains, damage infrastructure, and are very costly to control/eradicate learn more »

Giant Hogweed

A towering toxic invasive plant with WorkSafe BC regulations learn more »

European Fire Ant

A tiny ant with a toxic sting learn more »

Purple Loosestrife

An aggressive wetland invader that threatens plant and animal diversity learn more »

Orange Hawkweed

Also yellow, these invasive plants replace native vegetation along roadsides, and threaten areas not yet reforested learn more »

Japanese Knotweed

Grows aggressively through concrete, impacting roads and house foundations learn more »

Spotted Knapweed

A single plant spreads rapidly with up to 140,000 seeds per square metre learn more »

Scotch Broom

An evergreen shrub that invades rangelands, replaces forage plants, causes allergies in people, and is a serious competitor to conifer seedlings learn more »

Invasive species continues to spread despite supposed obstacles

BALTIMORE - Hardy, adaptable and prolific. We should all be so lucky. Instead, we are left to curse those traits in northern snakeheads, the toothy aliens that appeared by the hundreds in a tiny Crofton, Md., pond in 2002, touched off a national media frenzy and now have made themselves comfortable in the Potomac River.


"Thousands and thousands of them" call the Nation's River home, from Georgetown to Mount Vernon to where it empties into the Chesapeake Bay, said Steve Minkkinen, a U.S. Fish and Wildlife Service biologist.

The federal agency is preparing a plan to prevent snakehead colonies from infesting other bodies of water, beef up invasive species laws, encourage local rapid response teams and educate watermen and recreational anglers.

The Northern Snakehead Control and Management Plan was requested by Congress, whose members were alarmed by the "potential impact on native fish populations."

Their concern was well directed. Considering the fact that snakeheads, natives of Asia, weren't detected in the Potomac until 2004, the population explosion is both mind blowing and sobering. For recreational and tournament anglers, it raises questions about whether over time, snakeheads will eat largemouth bass out of house and home.

And it's not just here. Scientists say northern snakeheads are established in Pennsylvania and New York and small numbers of fish have been caught in California, Florida, Massachusetts and North Carolina.

If adopted by the Interior Department, the management plan recommends:

-Compiling research on snakeheads to better predict where they might become established

-Making anti-invasive species laws consistent and clear and establishing tough penalties

-Urging states to develop rapid response plans and containment procedures

-Evaluating eradication methods

-Creating a National Northern Snakehead website to disseminate information

Veteran Potomac bass guide Steve Chaconas, who worked on the management plan, said reeling in a snakehead five years ago "was rare. Now they're everywhere. I'm not catching 2-pounders anymore. The ones I'm catching now are in the 6- to 14-pound range."

The Crofton incident was both understandable and controllable. A man who kept two snakeheads in an aquarium with the idea of turning them into soup dumped them in the pond across the street when the fish grew too large and the dinner plan proved unpalatable.

The Department of Natural Resources eliminated the problem by poisoning the pond with the chemical Rotenone, scooping out the carcasses and restocking it with native Maryland fish at a cost of $110,000. Case closed.

But wresting control of the wide Potomac and its miles of tributaries from the grasp of snakeheads isn't that easy or cheap.

"You can't Rotenone the entire river," Minkkinen said. "The reality of the Potomac is we can't do anything about it. We're going to have a healthy population."

At one point, biologists believed that the deep, cold shipping channel in the middle of the Potomac would keep northern snakeheads pinned on the Virginia side. But they have been caught in the Anacostia River and Piscataway and Mattawoman creeks.

Then we were comforted by the news that higher salinity levels in the lower river would keep the fish bottled up. But watermen have found them in the Nanjemoy and St. Mary's rivers and St. Jerome Creek, past Point Lookout on the bay side.

"We don't know a lot about the snakehead and you can never really know what a species will do," says Joe Love, DNR's tidal bass manager.

It's not that biologists aren't trying. They have tracked them with radio telemetry and electrofished tributaries to get a handle on population density. Last year, Love, along with Fish and Wildlife's Maryland office, conducted a survey of where snakeheads and largemouth bass overlapped in habitat and diet.

Research concluded that the two fish liked to eat each other's offspring, live in shallow water beneath protective lilies and grass and chase frog baits.

Sounds like an old boyfriend.

Scientists say that when a "modest" number of snakeheads are removed from a stretch of water, the number and size of largemouth bass increased. What they can't predict is what will happen to the prey fish population with two voracious predators around and whether the "moderate" level of competition for food and shelter will escalate if the snakehead population continues to increase and expand.

Chaconas says he urges anglers to follow Maryland law and kill every snakehead they catch.

"Killing even one means it won't reproduce and you prevent it from being transplanted," he says. "Taking that fish out of the equation could be like killing 6,000."