Attack of the alien escargot

An invasion of New Zealand mud snails into Putah Creek is likely to lead to an emergency closure of a large stretch of the famed Northern California trout stream. The California Fish and Game Commission last week recommended a 120-day closure that is expected to be finalized next Tuesday and go into effect Jan. 1. The closure would take place on a six-mile stretch of the popular fly-fishing creek, which runs from Monticello Dam on Lake Berryessa east of Napa Valley to the Sacramento-San Joaquin River Delta.

The alien invaders -- no bigger than buckshot -- multiply quickly and spread rapidly along river bottoms. They can be transported from one waterway to another by fishermen, kayakers or others whose equipment comes in contact with the snails. They aren’t directly harmful to fish, but they eat nutritious invertebrates such as mayflies and stone flies which the fish need. Once established, the mud snails are extremely difficult to control.

Two years ago, they were discovered in California’s Owens River in the eastern Sierra.

“It’s potentially controllable at this stage,” said Ed Pert, a Department of Fish and Game biologist. However, he added, “if the Pandora is out of the box, there may be no reason to keep the creek closed.”

-- Pete Thomas