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Non-Native Weed Threatens Northwest Clams

  • Tom Banse

Japanese eelgrass smothering Willapa Bay clam beds in Sept. 2010.

Japanese eelgrass smothering Willapa Bay clam beds in Sept. 2010.

Japanese eelgrass has a devastating impact on yields

The usual story of invasive species goes something like this: an exotic plant or critter hitches a ride on some incoming cargo, alarm bells go off and an eradication campaign starts.

But now, Japanese eelgrass, a non-native seaweed showing up along America’s West Coast, breaks that mold.

Willapa Bay produces more shellfish for American tables than any other inlet on the West Coast. Brian Sheldon's family has been growing clams and oysters on the tide flats here for three generations.

"These little holes here are all clams. I call this my college fund bed," he says. "I tell my kids, you go out and work that bed, because that's how you're going to college."

But, Sheldon jokes, the way things are going that's shaping up to be an inexpensive state school rather than a plush private college.

Northern Oyster Co. owner Brain Sheldon says his business has been devastated by Japanese eelgrass.

Northern Oyster Co. owner Brain Sheldon says his business has been devastated by Japanese eelgrass.

His clam beds should be bare sand but Sheldon's acreage is being overrun by a green sea grass that really belongs on the other side of the Pacific.

"In the summer, this piece of ground here will be completely covered with grass," he says. "It kinds of sits in there and holds the heat in there in the bed and it makes the clams watery and weaker."

Sheldon calls it an infestation that has reached devastating proportions. Several neighboring companies have simply abandoned some of their clam beds.

"Our yields are down 40 to 50 percent, you know."

Marine biologists believe the Asian eelgrass was most likely brought to Washington State decades ago in shipments of oysters from Japan. The plant is also called Japonica or dwarf eelgrass. It has spread north to British Columbia and south along the Oregon coast into California.

Experimental application of herbicide (on right) controlled Japanese eelgrass, but its use is controversial.

Experimental application of herbicide (on right) controlled Japanese eelgrass, but its use is controversial.

Shellfish growers want Japanese eelgrass declared a noxious weed so they can spray herbicide or mow the invader down. California has already done so. To the growers, it seems obvious that Washington and its neighbors should do so as well. The sea grass is not native. It's causing a nuisance and there are control methods that work.

But not so fast, argue some marine scientists, state agencies and conservationists.

"In most areas of the world, these plants are highly protected. So in my mind, the ledger needs more examination," says Sandy Wyllie-Echeverria, a marine biologist with the University of Washington. "There are areas where Japonica has been shown to be a valuable resource and there are other areas where it is quite mixed."

In the Northwest, he says waterfowl like to eat the sea grass. A suite of smaller creatures probably lives and feeds in the vegetation. The eelgrass might also stabilize eroding beaches.

The Sierra Club also opposes eradication of the accidental colonist, even though it's non-native.

"For two reasons; one, it is fish habitat. But more importantly, in their efforts to eradicate Japanese eelgrass, there is a very high probability they could be eradicating native eelgrass," says the Sierra Club's Laura Hendricks. "That is something that would have a major impact on recovery of our fish species and the birds."

Caught in the middle is the Washington State Noxious Weed Control Board, which floats a possible compromise - list Japanese eelgrass as a noxious weed but only on commercial shellfish beds.

"It might not be the end-all, be-all solution that either side is looking for but what it does do is allow us to acknowledge it is a problem in one area, but it is not considered a problem in the other areas," says Alison Halpern, director of the panel.

Halpern's gotten some positive feedback, but not everyone's on board yet. Shellfish growers say it's a good start, but worry the plan could require them to fight the non-native sea grass into perpetuity.

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