Alan Martinez gets the willies just thinking about Sept. 14. That morning he received a call at his superintendent’s desk in the headquarters of Highline Lake State Park.
“We’ve got trouble,” the caller said.
Martinez, who has been at the park for 17 years, hopped in his truck without asking questions and headed for the west end of the lake. A small team of Colorado Parks and Wildlife aquatic inspectors had something to show him that, on a horror scale for wildlife professionals, was right up there with the Creature From the Black Lagoon.
It was a shelled aquatic critter not much bigger than Martinez’s pinkie fingernail. It was clinging to a piece of PVC pipe submerged in the waters of the popular boating, swimming and camping lake in the middle of Mesa County farm country not far from Colorado’s border with Utah.
The pipe had been dangling in the lake since the previous spring as part of CPW’s protocol for hunting for zebra mussels. They are fond of attaching to rigid submerged objects.
“It was sickening,” said Martinez, who, until that morning six months ago, had never seen a zebra mussel except in pictures. “At first, I was in denial: This can’t be happening here.”
He was well aware how much work had gone into preventing this mussel from invading Colorado for the previous 15 years. He also knew how many years of work and nail-biting worry were ahead because of this single mussel. It represented the first infestation in Colorado, a state that, in 2008, had passed the toughest “mussel free” legislation in the country to try to prevent this kind of thing from happening.
The invader, which likely hitched a ride to Highline on a boat, was rushed by pickup truck to CPW offices in Denver where lab tests that afternoon confirmed it was what it looked like.
State invasive species program manager Robert Walters, who had been fighting mussel invaders for a decade, had a similar reaction to Martinez on that end.
“I felt shocked and, yes, a little bit sick,” he said.
CPW briefly went into panic mode before countless meetings and planning sessions would birth a battle plan – all for a bean-sized bit of shell and tissue.
A half year of zebra-mussel headaches later – and with around a dozen more of the zebra mussel’s relatives turning up on rocks and boat slips at Highline – that plan moved into high gear this week.
The 563-acre Highline Lake had already been lowered this winter to 25% of its normal capacity to make mussel spotting easier and to freeze out any that might be lurking in the rocks along the shoreline.
Wednesday morning, in a mix of driving sleet and swirling snowflakes, a team of wildlife biologists looked like they might be the ones frozen out as they hopped into flat-bottomed jet boats and took to the diminished lake on what would normally be opening day for recreational boaters.
Outfitted with respirator masks, goggles and Tyvek suits over puffy jackets, they puttered around the lake’s perimeter pumping an ionic copper-based chemical called EarthTec QZ onto the surface of the water. The chemical has been used successfully in several other mussel-infested states and is designed to kill any mussels or mussel larvae that might be making a new home in the lake. It is also formulated to be less toxic to fish than other substances used to kill invasive species, partly because it can be diluted into a lower dose that is deadly for a mussel but not as dangerous to fish.
It works by blocking respiration at the cellular level for the mussels that breathe through tiny gills packed inside their shells along with minuscule organs and a single foot that can be deployed for moving around.
In five hours, the mussel massacre team applied 770 gallons of molluscicide. In two weeks, they will return for another round of spraying.
“I have really mixed feelings,” Walters said after a morning on the officially infested lake. “I wish we weren’t in this situation. It’s disappointing that we are where we are today. But we’ve done an incredible amount of planning leading up to this, and I feel really optimistic it will work.”
Zebra mussels present such huge problems in such tiny carapaces because they are so exceedingly clingy and so prolific at reproducing.
They are believed to have come to the U.S. by stowing away in the ballast of water on ships from the Caspian Sea in the late 1980s. Since then, they have spread throughout the Great Lakes and into drainages of the Mississippi River. Texas, Utah, Nevada, California and now Colorado claim infestations.
It is easy to understand how it happened. Female zebra mussels can each release a million eggs into bodies of water per year. Male mussels can release more than 200 million sperm in that same time to fertilize those eggs.
The fertilized eggs develop into larvae called veligers, which can be transported long distances by water currents. Within two to three weeks of conception, those veligers start forming the distinctive zebra mussel shells that have a unique D-shaped flat-bottom and black-and-white zigzag stripes.
They start attaching to underwater surfaces by using threadlike, protein-based strands that are tipped with a super glue-grade sticky surface. As many as 700,000 of the mussels can crowd onto a square meter, piling atop each other and literally sticking around in hard-to-dislodge, crusty mollusk mosh pits. They can clog up whatever they attach to – boat motors, dam intake pipes, docks, buoys, shoreline rocks – anything under the water surface.
They are huge eaters, so they gobble up plankton particles that are an important part of the diet of other invertebrates and small fish. The mussels also have an indirect effect on larger fish because all their vacuuming up of particles can make lake water so clear that the fish are easy pickings for birds and other visual predators.
If that’s not enough, mussels that wash up on shore can break into razor-sharp, foot-cutting bits on beaches that normally are covered in inviting sand. They can also scare off recreationists by stinking up shorelines. Their feces smells bad and so do the mussels that have died off after their two-to-five-year life span.
None of that nightmare scenario has happened at the 55-year-old Highline Lake. But the impacts are still substantial.
Waterfowl hunters were left high and dry this winter when the lake was lowered well below their blinds. Boaters who wait all winter to get back on the lake will have to wait awhile longer. An opening day for boating has not been set.
Once boats are allowed in, there will be some inconvenience. Inspections of boats coming into the lake will continue as they have in the past. But boat owners leaving the lake will likely encounter lines and delays as every boat will have to be decontaminated with a spray of 140-degree water – the temperature of not-quite-hot-enough coffee, but a level steaming enough to deal a death blow to invisible veligers.
Boaters are compelled to comply with this nuisance by House Bill 1008, known as the Mussel-free Colorado Act, that passed in 2018. It established increased penalties for not submitting to inspections or failing to register boats in the state. The act includes measures for prevention, monitoring, early detection, rapid response, education and long-term control.
State requirements also place a five-year equivalent of a scarlet letter on Highline Lake. Even if no more adult mussels or veligers are found after the dousing with chemicals, Highline won’t be able to shed its “infested” declaration until 2028.
Martinez said during those five years it will take a team of four full-time employees – including himself – to deal with the added decontamination measures.
The lake will likely be operating on restricted hours because of the staff’s extra decontamination duties.
“I have had boaters tell me that they will go elsewhere,” Martinez said in acknowledgment that the park he is so proud of will become something of a watery pariah.
For now, the good news is that at least one dock and intake pipes on the dam have not shown any signs of more mussels. Neither did inspections of 38 miles of an irrigation canal that feeds into Highline.
In other ironically good news for the lake, if a mussel infestation had to happen in Colorado, Highline was the best place for it, Martinez said. CPW owns the water in the lake, unlike most reservoirs in the state that are owned by irrigation companies. That made it possible to lower the lake level so drastically and to spray for the mussels.
“It would be a whole different ball of wax at most bodies of water in the state,” Martinez said.
Highline also had a plus for spraying because irrigation canals are shut down from Nov. 1 to April 1. No water comes in or leaves the lake during that time.
At least eight other lakes in Colorado have turned up zebra mussel veligers in lab inspections, but all those have passed the five-year mark with clean slates. None of those lakes ever dredged up an adult mussel.
Walters, who has been fighting other invasive species like New Zealand mudsnails and Eurasian watermilfoil along with mussels since 2012, recognizes that zebra mussels are the worst invasive foe he has yet faced. They have the potential to cause millions of dollars in damage if they get into dam intakes or systems of pipes. That’s why just a handful in an entire lake can be such cause for alarm.
That potential for zebra mussel monetary mayhem is why Walters and his crew were out in Highline this week trying the big step of essentially poisoning a lake. It is all they have to throw at this problem.
“We feel like we are putting all our energy into this,” Walters said. “We are doing the best we can.”
