For the first time in the six years since quagga mussels first appeared in Lake Powell, the alien mollusks are now clogging up boat engines, escalating fears that the prolific invaders could find their way into other popular lakes.
Wildlife officials in Utah and surrounding states are desperate to contain the epidemic because these mussels, which can proliferate unchecked in the absence of natural predators, encrust underwater fixtures and disrupt ecosystems.
Accordingly, boats exiting Lake Powell at Bullfrog, Halls Crossing, Wahweap and other ramps are inspected for quagga mussels. This year, more and more boats are found carrying the mussel or its larva, known as veligers, necessitating lengthy decontaminations that have forced boaters to wait for up to four hours.
“If you boat at Lake Powell, it’s very likely your boat has quagga mussels on it,” said Nathan Owens, aquatic invasive species coordinator with the Utah Division of Wildlife Resources. “With more mussels in the lake and lower water levels, more boaters have mussels attached to their vessels than in past years.
"Our techs are regularly finding them on and in boats that have only been in Lake Powell for a day or two — something we haven’t experienced in the past.”
The cause of alarm is the influx of adult quagga mussels, which are more likely to survive a ride to another lake than a veliger and are more capable of reproducing if they get there. But that assumes the mollusks are alive when they get into a boat.
The National Park Service, which administers Lake Powell, believes the problem may not be as dire as it seems. Most of the adult mussels floating in the water are dead, casualties of dropping lake levels that have left millions of them attached to dry rock, according to Billy Shott, superintendent of Glen Canyon National Recreation Area.
Dead quagga mussels drop off the sandstone walls into the water, where they get sucked into or washed onto boats.
“Those full-grown mussels, albeit dead, are much more prevalent in the water than in the past,” said Shott, who has plenty of firsthand experience from recreating in Powell’s wake-free bays.
“Periodically they show up on my paddleboard or bathing suit,” Shott said. “Dead quagga kind of smell like dead fish. They are very noticeable. Those are the same dead quagga showing up in boats.
“We don’t think they pose a threat,” he continued, “but in our inspection protocols, if the inspector sees quagga, that triggers a decontamination. It takes more time to clean, especially when they turn up in things like [boat] sea strainers. They also show up in holds where people keep their ropes and anchors.”
Taking no chances, DWR is inspecting more boats than ever. As of July 30, its staff, in partnership with the park service, had inspected 47,000 boats exiting Powell this year and decontaminated 3,100, far outpacing last year’s portion that were infested.
Technicians flush hot water through contaminated boats’ power systems, clean out their sea strainers, and pull bilge plugs. To avoid damaging internal systems, the water cannot exceed 140 degrees. Infected vessels with ballast tanks and inboard motors face a 30-day dry time.
“We want to make sure it’s done the same way every time,” said Lt. Scott Dalebout, DWR enforcement officer in charge of quagga. “We are trying to get folks to plan their exit better, so people don’t wait until the last minute to come off.”
The bottlenecks have frustrated many visitors, and this holiday weekend, DWR is deploying more crews to Powell so inspection waits won’t be as long.
“Ours and Utah’s employees on the ramps are doing a tremendous job,” Shott said. “I feel terrible they are taking the brunt of this. You can imagine what it’s like working a 10-hour shift in 105-degree temperatures, and you are catching a visitor who just had a great weekend, and they are going to be in a rush to get home.”
Elsewhere in the state, DWR inspects boats before they enter Bear and other Utah lakes. Officials have stopped more than 120 infested boats this year, quarantining 100 of them.
Scientists are tracking quagga mussels' ecological impact, and so far it’s looking like a mixed bag at Lake Powell, according to Ken Hyde, Glen Canyon’s science chief.
The mollusks extract heavy metals from the water, accumulating these toxins in their bodies. Bluegill, sunfish and some waterfowl are able to eat them despite their hard shells.
“Coots and goldeneyes will eat them off the docks,” Hyde said. “We are just learning how to live with these things.”