PHOENIX — A tiny European shellfish whose larvae are swarming the Colorado River and connected water bodies has colonized reservoirs and canals in the hills around the Phoenix area.
Officials fear the invaders could clog treatment plants and require millions of dollars in local pest control — possibly hundreds of millions when the costs are spread from Lake Powell to Los Angeles. A losing battle means plugged pipes and, out in the lakes, slow fishing.
Quagga mussels were first introduced in this country by an accidental release from a tanker’s ballast water into the Great Lakes back in the 1980s. They have expanded rapidly through the Southwest since their discovery at Lake Mead nine years ago.
They’re most likely here to stay, setting up a perpetual battle.
“By the time they’re detected it’s too late,” said Colleen Allen, an invasive-species specialist at Glen Canyon National Recreation Area, where quagga mussels by the millions are colonizing submerged cliffs and houseboat hulls.
“There’s nothing you can do to eradicate them.”
That leaves the states, federal agencies and municipal water suppliers to scrape, heat and dose them with chemicals to keep them in check.
The filter feeders could ruin a prized striped bass fishery at Lake Powell and starve numerous smaller fishing holes.
A RAPID SPREAD
The fingernail-size bivalves already have spent almost a decade in the Central Arizona Project canal and Lake Pleasant north of Phoenix. Now they have reached Canyon Lake in the hills on the city’s east.
The Arizona Game and Fish Department in December discovered a mussel on a boat that had moored in the reservoir, and tests confirmed larvae in the water.
But the quaggas haven't yet crashed the ecological web that supports sportfishing in Arizona reservoirs or choked-off pipes and water intakes in what officials fear will be a repeat of their billion-dollar destructive path through the Great Lakes.
They can rob the water of nutrients that can support fish. They stick to each other, piling up in clumps that clog pipes and dam intakes. They overheat boat motors if sportsmen don’t notice they’ve blocked the water that cools them.
The state is scrambling to keep boat owners from moving them to new waters in their bilge.
“They rapidly colonized a lot of the pipes, water-delivery systems, intakes,” said Shawn Gerstenberger, dean of community health sciences at University of Nevada-Las Vegas. “They require routine, regular and very costly maintenance.”
Parts of Lake Mead have notably clearer water now, he said, though the effect on fish that thrive in murkier, plankton-rich waters there remain uncertain. Hoover Dam employees must routinely pull up submerged debris screens to remove mussels and keep water flowing through the hydropower turbines.
After quaggas turned up in Lake Mead in January 2007, state and federal agencies launched a defensive front to keep boaters from transporting them to new waters. They demanded thorough cleaning of boats that left the lake, and emptying and drying of boat motors and tanks where wet larvae could survive until splashing down in new waters.
When divers went looking for mussels elsewhere, though, they found it was too late.
By the end of 2007, the mussels had established downstream of Hoover Dam, in Lake Havasu and Lake Mohave, and eastward through the Central Arizona Project Canal. They were in Lake Pleasant, a CAP reservoir on the edge of Peoria and a metro Phoenix fishing and boating hot spot.
MENACE TO BOATERS AND NATURE
Boaters at Lake Pleasant have become accustomed to the mussels, routinely pulling their boat plugs when leaving the water, or watching where they step, to avoid sharp shells.
Not all are entirely sure there’s anything to be done to prevent them from infesting new waters, though, such as the Phoenix area’s biggest reservoir, behind Roosevelt Dam on the Salt River.
“What are they going to do, start washing birds’ feet?” said Josh Punko, a 40-year-old Phoenix resident who was launching his bass boat Wednesday at Lake Pleasant with his wife and daughter.
He wishes the mussels could be controlled — “You don’t want to swim without shoes on!” — but he’s not sure boating restrictions will matter.
Punko wore a Lake Powell T-shirt and said he’s most irritated by the National Park Service’s policing of boat traffic to and from that reservoir, which was found to be infested with larvae in 2012 and adult mussels in 2013. He recalled waiting with 100 or more other boaters on the boat ramp in 110-degree heat while officers inspected boats for anything wet.
“It makes it a real pain to go fishing,” he said.
So far, budget constraints in Arizona have prevented that kind of vigilance at state-monitored lakes. Lake Pleasant boat ramps include tall signs saying, “Don’t move a mussel,” and asking boaters to dry their boats for five days before entering another lake.
Punko planned to fish Saguaro Lake the next day. That Salt River Project reservoir east of Phoenix, although upstream of the recently infested Canyon Lake, is considered affected because of a hydroelectric pump-back system that mixes water — and likely larvae — between the two.
Lake Powell straddles the Arizona-Utah boundary, tucked into more than 1 million acres of cliffs and canyons behind Glen Canyon Dam. The lake is the nation’s second-largest reservoir and a petri dish showing how rapidly quaggas can spread. Scientists believe they’re especially prolific in the Southwest’s warmth, which allows them to reproduce several times a year.
WORKING WITH PUTTY KNIVES
Across the Southwest, the invaders are changing business for water providers. In Las Vegas, the Southern Nevada Water Authority had to add pipes to mix ammonia and chlorine at its new, billion-dollar deepwater intake in Lake Mead, killing veligers before they enter the system.
The annual cost for chemicals is about $50,000, a spokesman said.
In metro Phoenix, SRP first found mussels in 2008 at a canal that allows for water exchanges between its system and the CAP canal. Since then the East Valley water provider has found mussels around the Tempe water treatment plant and now must scrape them off with a putty knife, from there and throughout the canal system during annual dry-up cleanings.
“We try to physically remove them as a way of knocking back their population so they don’t start impacting operations,” SRP environmental scientist Brian Moorhead said.
So far the mussels have not caused major problems in SRP canals or on headgates and have attached mostly under bridges or structures limiting sunlight penetration. “Their numbers have not taken off as we feared,” Moorhead said.
If they proliferate, he said, municipalities might need to consider adding trace copper to their treatment plants to help kill the larvae.
Although the spread has been rapid and seemingly unabated, state officials say there’s still value in trying.
The Arizona Game and Fish Department provides mobile decontamination units — heated water sprayers — at Lake Pleasant and Lake Havasu, and aquatic-invasive-species coordinator Tom McMahon recommended using them.
“This is just one invasive species,” he said, though it moves in the same waters that transport others from around the world.
“If we battle this one as hard as we can, most likely we’ll keep out other invasive species that we wouldn’t want.”
