An invasion of exotic zebra mussels was fended off earlier this month at – of all places – an interstate weigh station.
A sharp-eyed commercial vehicle inspector spotted the tiny mollusks clinging to a 38-foot yacht being hauled into Washington behind a semi truck, said Capt. Mike Whorton, regional enforcement supervisor for the Washington Department of Fish and Wildlife.
Rather than breathing a sigh of relief, Department of Fish and Wildlife officials say the discovery is just a preview of what’s expected to come with the influx of visitors for the bicentennial of the Lewis and Clark Expedition. Many are expected to head west with a boat behind their RV or pickup truck. Private vehicles are not required to stop for inspection, Whorton added.
“Every western state is concerned,” Whorton said. “The impacts if they get here are huge. It’s the AIDS of the waterways. Once you get them in there, there’s no feasible way to get them out.”
Washington State Patrol and Fish and Wildlife officers have spotted zebra mussels on at least two other incoming boats, Whorton said. The thumbnail-sized mussels can survive nearly a week out of the water and even longer if they are inside a boat’s bilge tanks. Larval zebra mussels are impossible to spot.
The most recent find was made on May 11 by inspector James Spencer at the Interstate 90 port of entry between Post Falls and Spokane. With help from Spokane Police Officer Brian Baldwin, Spencer detained the boat hauler until Whorton and another Fish and Wildlife officer arrived for further inspection. The boat was sent to a decontamination site at a Bellingham marina.
The owner had attempted to clean the boat, but not thoroughly enough, Whorton said.
Washington has been on the lookout for zebra mussels for the past four years, said Pam Meacham, assistant coordinator for the Fish and Wildlife department’s aquatic invasive species program. Commercial vehicle inspectors have been trained to look for the creatures.
“So far, Washington is free of zebra mussels,” she said.
Idaho also is watching, said Capt. Steve Agte, regional enforcement chief for the state’s Department of Fish and Game. “We’re very concerned about it.”
Plastic tubes have been placed in Idaho’s major lakes and waterways as a way to provide an early warning of zebra mussel presence, said Ned Horner, regional fisheries manager for the Department of Fish and Game. The tubes have been rigged with a special mesh that biologists believe will be an attractive, colonizing site for juvenile mussels. The tubes are checked regularly, Horner said. To date, they remain mussel-free.
“Unfortunately if they show up, it’s probably too late,” Horner said.
Once introduced, the mussels are impossible to eradicate, according to the U.S. Geological Survey. They eventually colonize everything from boats, docks and water intake pipes to slow-moving crayfish and clams.
The U.S. Geological Survey estimates the mussels will cause $5 billion in damage to fisheries and commercial water supplies over the next decade. One town in Michigan had its water supply choked off for three days after its intake pipes became clogged with the mollusks.
The mussels are native to Central Asia and Russia, and hitched a ride across the Atlantic in the ballast of a ship. They were first spotted near Detroit in 1988 and have since spread to waterways in 22 states, according to a fact sheet from the U.S. Geological Survey. The mussels were most recently discovered in parts of South Dakota and Kansas.
A curious side effect of the mussels has been the clarification of water in the Great Lakes. Each adult mussel filters up to a gallon of water per day in search of a meal of plankton. They also filter out other impurities. With portions of Lake Erie home to up to a million mussels per square meter, clarity has gone from less than 6 inches to more than 30 feet.
Plankton serves as the food pyramid’s foundation for lake life. Zebra mussels have essentially vacuumed vast swaths of the lake, Horner said.
“It all goes to the zebra mussels,” he said. “The lake turns into a desert.”
The same could happen in the West. With entire economies and ecosystems based on fisheries, much is at stake. Larger boats being hauled by commercial trucks will continue to be inspected, but there are no plans to begin widespread inspection of incoming private vehicles pulling boats from the Midwest. Officers have neither the time nor the eye power to properly inspect each boat, Washington and Idaho officials say.
The best defense is education programs, Horner said. Many anglers in the Midwest are already well aware of the dangers of zebra mussels. But all it would take is one boat carrying a few tiny mussels to unleash a new scourge on the waters of the West.
“The boats that don’t stop at the weigh stations – the smaller trailered boats – that’s where it’s going to come in,” Horner said, adding. “I’m not real encouraged that we can keep them out.”
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