A state boat-decontamination crew Wednesday discovered the first non-native zebra mussels in Oregon at the Ashland Port of Entry on Interstate 5 during a voluntary inspection of a boat previously passed as clean in California, authorities said.

A state boat-decontamination crew Wednesday discovered the first non-native zebra mussels in Oregon at the Ashland Port of Entry on Interstate 5 during a voluntary inspection of a boat previously passed as clean in California, authorities said.

More than two dozen of the mussels, which could invade Oregon waterways and cost millions annually to control in the Great Lakes and elsewhere, were found on the motor of a 15-foot Boston whaler whose owner stopped for a voluntary inspection at the port of entry about 11 a.m.

"It was a shock to see them as plain as day," said Sam Dodenhoff, part of the two-man Oregon Department of Fish and Wildlife inspection team. "We've done a lot of inspections and we've never seen anything like this."

The inspection team is one of five around Oregon that go to boat ramps and ports of entry to hold voluntary boat inspections under an invasive species prevention program begun last year and funded through a $5 annual permit needed to launch any boat over 10 feet long in Oregon waters.

The boat's owner, an unidentified Washington man, said he was transporting the boat from Arizona to his home in Everett, said Rick Boatner, the ODFW's aquatic invasive species coordinator.

Boatner said the owner reported he bought the boat on eBay from someone in Michigan, where the mussels are a persistent problem.

Dodenhoff said the boat owner was aware of Oregon's volunteer inspection program when he pulled over. The man said he did not know the mussels were present on the boat, in part because the boat was passed by inspectors as he traveled from Arizona into California, Dodenhoff said.

"I'm glad he stopped," Dodenhoff said. "It makes me wonder how many have driven by without us knowing."

The 2009 Oregon Legislature created the program but left participation mandatory because of a belief that it would be struck down as violating Oregon's ban on police checkpoints. Since then, a state Department of Justice opinion states that very specifically intended check stations could be mandatory and not violate the Oregon Constitution.

A bill is now working through the Oregon Senate that would make boat inspections mandatory.

The mussels were removed and kept for analysis while the boat was decontaminated with a hot wash before it was released, Boatner said.

ODFW crews on April 7 in Hood River did a similar decontamination of zebra mussels' cousins — quagga mussels — from a boat entering Oregon from Idaho. Those mussels were discovered by Idaho inspectors who were unable to disinfect the boat because of faulty equipment, so they notified ODFW officials about their presence, Boatner said.

Since arriving in the Great Lakes in the late 1980s, probably in the ballasts of ships, zebra and quagga mussels have infested the Colorado River system, including Lake Mead in Nevada. States around the West are taking steps to limit their spread because of the damage they inflict on hydroelectric dams, water diversions, treatment plants and irrigation systems.

Like many invaders, zebra and quagga mussels can thrive in non-native waters because nothing exists to keep them in check naturally.

Virtually impossible to eradicate, they reproduce exponentially and overtake entire lake bottoms. Great Lakes states spend millions of dollars annually just cleaning boat engines and water pipes of mussels.

Native to Eurasia, the mussels filter zooplankton, quickly altering ecosystems.

Reach reporter Mark Freeman at 541-776-4470 or email at mfreeman@mailtribune.com.