Montana waters set to move to mussel-free designation | 406 Politics

Montana Fish, Wildlife & Parks recently launched the delisting process for Tiber. The agency is taking public comment through March 25 and will hold an online public hearing next week to consider stripping “known existence of aquatic invasive mussels,” from the agency’s rulebook on invasive species.

In 2016 larvae called “veligers,” from either invasive zebra or quagga mussels, were detected during water sampling at Tiber. A suspected positive sample was also detected at Canyon Ferry Reservoir that same year.

The detections were the first in the state, drew a governor’s emergency declaration and quickly saw the Legislature fund a significantly beefed up watercraft inspection and water sampling program. Decontamination stations at the two reservoirs soon became a fact of life for boaters, increasing education campaigns such as the state’s “Clean, Drain, Dry,” program, and regulations mandating inspections for out-of-state boats and those traveling east to west over the Continental Divide aimed to protect mussel-free waters.

Waters infested with invasive mussels have seen a multitude of consequences, from negative impacts on fisheries and other aquatic life to significant costs associated with cleaning and keeping infrastructure clear of the mollusks. Estimates of a worst-case infestation in Montana put costs north of $200 million.

But the detection of veligers does not always lead to the detection of an adult population, as veligers may be transported on watercraft or a few adults might release veligers but ultimately fail to breed due to environmental reasons.

The accepted method of testing for mussels involves a fine-mesh net followed by an inspection of its contents under a microscope. Since those first samples at Tiber and Canyon Ferry, the state has analyzed thousands of samples without another positive detection.

A newer method, analysis of eDNA, is growing in detection applications as well, but microscopic analysis remains the current standard.

With Canyon Ferry designated a suspected positive based on a single sample, three years of negative samples allowed the reservoir to be delisted in 2019. The three-year mark is based on the known biology of mussels and the likelihood that if they were present, adult mussels would have been found.

The bar is higher with positive samples from Tiber, requiring five years of negatives to qualify for delisting after more than one sample tested positive for veligers.

“We’d be considered nationally mussel-free,” said Thomas Woolf, FWP’s aquatic invasive species bureau chief. “Because we’ve not had that evidence (of mussels) for five years, it’s something where we may have dodged a bullet.”

Woolf noted that Colorado has seen waterbodies go through the same multi-year quarantine process as Canyon Ferry and Tiber, be delisted and remain mussel-free.

The news around aquatic invasive species is not all good, however, as inspectors stopped a record number of boats coming into Montana carrying adult mussels. And last year an unlikely source, aquarium moss, was found containing mussels.

“The data tells us we still see a threat coming,” Woolf said. “Mussel-free doesn’t change the vectors coming into the state, and it’s important that we continue to address it.”

With boating season quickly approaching, a few inspection stations are already open. Removing Tiber from a positive waterbody designation will allow a shifting of resources to other stations, Woolf said, and some new stations run by conservation districts are also slated to come online this year.

Steve Harada, executive director of Montana Walleyes Unlimited, believed the removal of Tiber is a positive development.

“I think it’s a good deal for sure,” he said. “For one thing it’ll make access easier, and it’s all about getting people out fishing.”

Harada has worked as a tournament director on Fort Peck where anglers have incorporated extra protocols with FWP to clean boats. He believes the design of Montana’s program has been good, for example allowing watercraft to be inspected at border stations such as Wibaux before coming into the state. The organization will continue to support invasive species prevention with its mission of enhancing warm water fisheries.

The federal Bureau of Reclamation operates Tiber Dam. Resource division manager Jeff Baumberger said that following the positive detection the bureau conducted inspections of the dam face and riprap. The bureau had previously conducted water sampling for invasive species and will keep at it, he said.

“We will continue to operate Tiber Reservoir as we have in the past, and there are no restrictions on the reservoir,” he said. “We’re happy it’s negative for sure, and we’re hoping it stays that way.”