Stamping out infestations
Researchers to smother non-native clams in lake
University of Idaho researchers hope to stamp out an infestation of Asian clams in Lake Pend Oreille by smothering them.
Beginning this weekend, they’ll be sprinkling lye pellets on the lake’s bottom near Ellisport Bay in Hope, Idaho, and placing rubber mats over the pellets. Together, the pellets and the mats create a low-oxygen, alkaline environment that’s been effective at killing the clams in other locations.
About a half acre of Lake Pend Oreille is infested with the non-native clams, which have spread to the south since they were first detected in the lake in 2012.
“We’re fairly concerned that they are on the move,” said Frank Wilhelm, associate professor in UI’s Department of Fish and Wildlife Sciences. “We want to nip this in the bud … because of their impact on water quality.”
Asian clams have spread rapidly throughout North America since they were first discovered in the Western U.S. in 1938. The clams also are found in parts of the Snake and Lower Columbia rivers, but they appear to be most destructive in freshwater lakes, which is why their presence in Idaho’s largest lake concerns officials and local citizens.
“The lake’s our livelihood,” said Lisa Derr, general manager for the Pend Oreille Shores Resort, a time-share condo development in Ellisport Bay.
Since the clams were discovered near the resort’s dock during a milfoil survey, the resort’s board of directors and its employees have taken a proactive approach. The resort welcomes monitoring on its property, Derr said. And through newsletters and conversations, the staff works to educate time-share owners and their guests about the importance of sanitizing boats to reduce the spread of invasive species.
Everyone has a vested interest in protecting the lake’s water quality, she said. “It’s a precious resource.”
After they were found in Lake Tahoe in 2002, Asian clams spread to densities of more than 3,000 per square meter in parts of the lake. Scientists blame the clams for algae outbreaks that have fouled the pristine lake in the Sierra Nevadas that straddles the California-Nevada border.
The clams filter the water, sucking out the algae and excreting highly concentrated nutrients that promote further algae growth, said UI’s Wilhelm.
Asian clams are also bad for recreation, because of the profusion of sharp shells that wash up on beaches.
The mats in Lake Pend Oreille will remain in place until mid-April. Over time, carbon will mix with the lye in the pellets, neutralizing the solution until it’s benign, Wilhelm said.
UI is working closely with federal, state and local agencies on the clam suppression project. Citizens who want to volunteer to help with monitoring can learn more at webpages.uidaho. edu/LPOAsianclams.