OLYMPIA - Capitol Lake is closed to public use of any kind until further notice because of the discovery of an invasive species - the New Zealand mudsnail.
The tiny creature, which measures about 1/8 inch, was found in large areas of the north basin of the 260-acre lake and has been spotted in concentrations as high as tens of thousands per square meter, said Allen Pleus, state Department of Fish and Wildlife aquatic invasive species coordinator.
“Based on those concentrations, it’s probably been in the lake about two years,” Pleus said.
Small and hard to detect, it was spotted by Olympia resident Bert Bartleson during a bird-watching trip last month. The infestation was confirmed by Fish and Wildlife surveys of the area.
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The lake closure invoked Wednesday by the state Department of General Administration, the agency that manages the man-made lake, bans all forms of water contact by the public and pets.
The lake closure is limited to water contact. The trails and parks around the lake remain open to the public.
“These tiny snails can be transported in a pant cuff, on boots, kayak equipment or in your dog’s foot pads or fur,” Pleus said. “That’s why we need the public’s support in preventing the problem from spreading to other waters.”
It is a gross misdemeanor to possess or transport an invasive species, even accidentally, Pleus said.
“We’ll be ramping up patrols around the lake,” said Eric Anderson, a Fish and Wildlife enforcement officer assigned to invasive species control. “Our number one priority is to educate the public – we don’t want the snail to spread.”
First introduced to the United States in the 1980s, the snail has gained a foothold in the western part of the country, including the lower Columbia River and freshwater canals on the Long Beach Peninsula. Officials will probably never know how it infested Capitol Lake.
It thrives in freshwater, but tolerates brackish water, too, Fish and Wildlife policy analyst Bill Tweit said.
The biggest environmental threat the species poses is its ability to wreak havoc at the bottom of the aquatic food chain, out-competing native snails, mussels and invertebrates that are crucial food for fish and other aquatic life. The first priority is to contain what is the first New Zealand mudsnail infestation in the Puget Sound region, Pleus said.
In the next few weeks, crews will conduct snail surveys in the Deschutes River, Percival Creek and Black Lake, which are all part of the Capitol Lake drainage system.
Options to control or eradicate the invasive species include biological and chemical methods, but no decision has been made on how to approach the problem, Pleus said.
The state Department of General Administration will post lake closure signs around the shoreline as soon as next week, agency planner Nathaniel Jones said.
It’s unlikely the lake will reopen to the public until state agencies install washing stations on the lake shore for people to hose off their boats, dogs and other equipment, Pleus said.
“The closure could be for a few months – not years,” he said.
John Dodge: 360-754-5444