Alien invaders? Alert is on for mitten crabs

ASTORIA, Ore. — In Asia, they're considered a delicacy. In America, they're considered deadly. Fortunately, only one of them has been discovered in the Columbia River region — and new laws are aimed at keeping any more out.

But fears remain that the Asian mitten crab, an invasive, migrating crustacean, will bury its furry claws into the Northwest's precious waterways and economy.

Named for the thick clumps of hairlike threads on its pincers, the mitten crab is the target of research and educational efforts along the West Coast.

Researchers in the Northwest are especially focused on the Columbia River, where they fear the creature — which spawns in salt water and can migrate hundreds of miles up rivers — could cause problems similar to damage already caused in California.

The unwelcome alien first arrived in the San Francisco Bay in 1992. Within a decade, nearby rivers and fisheries have been devastated with clogged fish screens, eroded banks and levees, and marred commercial-fishing nets.

Researchers have confirmed that the crabs eat steelhead eggs and suspect them of eating salmon, sturgeon and trout eggs as well.

"They're really one of the last things we want to see in the Columbia," said Toni Pennington, aquatic nuisance-species research assistant at Portland State University's (PSU) Center for Lakes and Reservoirs.

"Salmon already have enough problems around here."

The crabs are also known to carry the Oriental lung fluke, which can be passed to humans and causes symptoms similar to tuberculosis.

Pennington and others at PSU are working to ensure that if the crab makes it to the Columbia, someone notices. She's traveled much of the Oregon coast posting "wanted" signs for the species, which urge anyone finding one of the crabs to kill it and report it to Oregon's invasive species hot line: 866-INVADER.

With female mitten crabs carrying between 250,000 and 1 million eggs, "even seeing one crab is a serious alert," Pennington said.

California's San Joaquin Delta is a frightening example. Four crabs were discovered in the delta in 1996. By the following year, their population was estimated at about 20,000, and it has grown since.

"It's true, they can produce in horrendous numbers under the right conditions," said Jim Bergeron, a retired Sea Grant extension agent, who has helped with local monitoring efforts. "(But) there really isn't a whole heck of a lot you can do if they do show up here. "The focus is prevention and testing to give people warning."

These days, four teams of nine volunteers intermittently check traps around the lower Columbia and tributaries, as they have since late last year.

Efforts are also being made to educate fishermen, who likely have the best chances of accidentally snagging one of the crabs or spotting one of its burrows.

"In most cases, it's the public, like a fisherman, that finds one and say. 'Hey, what's this?' " said Scott Smith, aquatic nuisance-species coordinator with the Washington Department of Fish and Wildlife. "Those are the people we're counting on."

Fisheries groups are also readily offering their assistance.

"When an invader comes into a new territory, it reaches beyond a single species," said Stephen Phillips with the Pacific States Marine Fisheries Commission.