Snail Pest Is Discovered in Another River

The New Zealand mud snail has been found in a second Northern California river, state wildlife officials said Friday, dashing the hopes of California trout enthusiasts who had hoped to quickly contain the fast-breeding mollusk to a single West Coast waterway.

The news came just as biologists said one of the waterways -- Putah Creek, east of the Napa Valley -- was experiencing its first true salmon run in a generation downstream from the snail infestation.

Fishermen and wildlife officials fear the tiny mud snail because it can reach concentrations of a million per square meter, driving out much of the native invertebrate population on which fish feed.

It has affected famous Western trout streams such as Montana’s Madison River and the Snake River in Idaho, but until this fall had been found only east of the Sierra Nevada range, including the Owens River and Hot Creek in California.

On Friday, the state officially closed a section of Putah Creek, one of Northern California’s prime trophy trout streams. The closing affects an area from Monticello Dam on Lake Berryessa Reservoir east of Napa Valley downstream to, and including, Lake Solano in Yolo County.

The fishing ban will last 120 days as biologists try to determine how far the snail has spread there and what, if anything, they can do to eradicate it. But biologists already have found the snail in wetlands along the creek, meaning “it would be nearly impossible to eradicate,” said Steve Martarano, a spokesman for the state Department of Fish and Game.

“They’re in all these nooks and crannies, so how do you get them all?” Martarano said.

Wildlife officials also announced that the snail had been found about 40 miles away in the Mokelumme River, which flows from the Sierra Nevada south of Sacramento. An East Bay Municipal Utilities District crew found the snails on equipment downstream from Camanche Reservoir, east of Lodi.

Both waterways eventually empty into the Sacramento-San Joaquin River Delta.