OLYMPIA - State officials drew down Capitol Lake two feet Wednesday night to test whether below-freezing temperatures will kill the New Zealand mudsnails that have invaded the lake.
The lake drawdown came at the request of state Department of Fish and Wildlife biologists looking to get a leg up on the miniscule creatures discovered in the lake last month.
The invasive species can reproduce rapidly and disrupt the bottom of the aquatic food chain.
Its presence triggered a ban on public use of the lake Nov. 25 until further notice while biologists grapple with a plan to control and eradicate the tiny creatures.
The snails, which are about one-eighth of an inch long, have been spotted in concentrations as high as tens of thousands per square meter along the lake shoreline, primarily in the north basin of the 260-acre man-made lake, state Fish and Wildlife biologist Allen Pleus has said.
The snail has no natural predators but doesn’t tolerate sub-freezing temperatures well, according to a Utah Department of Agriculture fact sheet.
The snail’s temperature tolerance range is listed at 33 to 77 degrees. The National Weather Service predicted temperatures in the low teens overnight in Olympia. “When they are exposed to freezing temperatures, they will die,” Pleus said.
But the snail can burrow in the sediments, which might afford it protection against the drawdown.
Fish and Wildlife biologists will be at the lake today, checking on the effectiveness of the drawdown.
Fish and Wildlife officials asked the state Department of General Administration for a complete drawdown of the lake Monday, but the state agency that manages the lake was hesitant to take action without more proof that doing so would kill the snails, said Jim Erskine, a spokesman for General Administration.
“We’ve been exploring all our options,” Pleus said.
Late Wednesday, agency director Linda Bremer approved the partial drawdown for two or three days, Erskine said.
John Dodge: 360-754-5444