A pontoon boat carrying the invasive quagga mussel was intercepted Friday morning at the main boat ramp of McPhee Reservoir.

Colorado Parks and Wildlife inspectors stopped the boat before it entered the water.

Lake managers began stricter access protocols this year to prevent contamination by the mussel, which can clog irrigation equipment and cannot be eradicated from a waterway. Motorized, trailered boats can only access the lake through boat inspection stations at McPhee and House Creek boat ramps during open hours.

The infected boat caught Friday was secured in a yard until it can be decontaminated.

Parks and Wildlife spokesman Joe Lewandowski said the owner told officials he bought the engine on Craig’s List, but became suspicious when he learned it was from Lake Powell, which is infested with the mussel.

It’s the third boat this year that has showed up in Southwest Colorado with adult mussels. In April, Parks and Wildlife quarantined a houseboat parked on Mancos Hill, and another boat showed up at Ridgway Reservoir.

“We are surrounded by states positive with the mussel, and preventing them here will take great vigilance,” Lewandowski said.

Lakes in Utah and Arizona are infected with the mussel, and some prevention regulations depend on boat owners’ action.

Boaters should drain, clean and dry boats before and after leaving any waterway. Mussel larvae can survive 28 days in standing water.