Report says invasive mussels pose economic, ecological threats

For a region rich in lakes, the specter of infestation by invasive mussels can wring shudders from people familiar with what’s at stake.

Threatened resources include premier fisheries, recreation, infrastructure, lakeshore property values and related tax revenues.

On Thursday, the Montana Invasive Species Council released a report that suggests Montana’s economy would be hit with more than $230 million in annual mitigation costs and lost revenue if invasive mussels become established in the state.

And that figure doesn’t include “ripple effects and indirect costs,” said Stephanie Hester of the Montana Department of Natural Resources and Conservation. Hester is coordinator of the Montana Invasive Species Council.

Bryce Christiaens, council chairman, said the total impact to the state “would be considerably higher.”

Robin Steinkraus, executive director of the Flathead Lakers, said the economic costs study confirms the importance of preventing the spread of invasive mussels and demonstrates the wisdom and value of related investments.

“It shows the value of our best defense, the watercraft inspection stations at the state borders, at Tiber and Canyon Ferry reservoirs, and in the Flathead,” Steinkraus said. “Those stations need to be open longer hours and for a longer season to reduce the risk of mussel introductions and prevent the enormous annual costs associated with mussels.”

She added, “Zebra or quagga mussels in Flathead Lake and other water bodies would change them forever. The indirect costs not included in the estimate of direct damages would include irreversible damage to our lakes and the aquatic life they currently support, to connected ecosystems and to the enjoyment they now provide us.

Not included in the $234 million are potential costs associated with ecological damages to native species, lost jobs and the personal and cultural benefits people derive from lakes and rivers, the council said.

It estimates that losses to lakeshore property values from diminished aesthetics and other impacts would total nearly half a billion dollars, with associated effects on property tax revenue.

“Invasive mussels can devastate aquatic ecosystems, clog water intake pipes and delivery systems, cover boat launches and beaches and impact any economic sector dependent on water,” Christiaens said.

The Montana Department of Fish, Wildlife and Parks has been working since 2005 to try to prevent the introduction of invasive mussels. The department’s interventions include inspecting watercraft, early detection monitoring and education.

These efforts intensified after larvae of invasive mussels were detected at Tiber Reservoir, with a suspected detection at Canyon Ferry Reservoir. So far, no adult mussels have been found and no more larvae have been detected.

Thomas Woolf, the Aquatic Invasive Species bureau chief for Fish, Wildlife and Parks, said eradicating invasive mussels once they’re established “is difficult if not impossible.”

Woolf said prevention is the best approach.

“Research continues on methods to prevent and manage mussels, so the longer we can keep them out, the better the chances we’ll see a solution to this problem,” he said.

Annual funding in Montana for Aquatic Invasive Species prevention, monitoring and education is $6.5 million.

Hester said that there are bills this session before the state legislature related to the Aquatic Invasive Species efforts but no request at this point that funding be increased.

Zebra and quagga mussels are invasive freshwater mussels discovered in the Great Lakes in the mid-1980s. Infestations can cause the extinction of many native mollusks, change the structure of food webs and contribute to the collapse of valuable sport fish populations, according to the council’s report on economic costs.

Liz Lodman, coordinator for Fish, Wildlife and Parks’ Aquatic Invasive Species program, said invasive mussels disrupt the food chain because they can filter so much water and remove food that fish and other aquatic life would eat. She said mussels also can cover areas where fish once laid eggs.

Dense concentrations of mussels also can clog pipelines and water intakes and disrupt operations at hydroelectric power plants and municipal water plants.

Mussels can grow on boat hulls, engines and steering components.

“Beaches can become unusable due to the sharp shells and pungent odors of dead mussels washing ashore,” the report said.

Steinkraus said her organization has long been focused on the damage invasive mussels could do to the region.

“Increasing awareness of this threat and strengthening state and local prevention programs has been a top priority of the Flathead Lakers for over a decade,” she said.