Invasive Harm Local Fish at Loch Lomond Marina

Since 2006, crews have squatted along the muddy banks of the marina, painstakingly finding the cone-shaped Japanese snails -- which in some cases are the length of a pea or smaller -- and placing them in bags. Later, they are frozen to death.

Despite the effort in 2006, when roughly 85,000 snails were hauled in, by 2007 the hard-shelled mollusks had spread tenfold and are thriving again this year.

"Last year, we discovered it had spread," said Chela Zabin, ecologist with the Smithsonian Environmental Research Center based in Tiburon, which is helping lead the effort. "They are still here. This is a very good season for snails."

Zabin and a half-dozen others were out at low tide Monday, sitting and picking the snails one by one.

"As you can imagine, it's extremely tedious," Zabin said.

But it's important.

The snail -- Batillaria attramentaria -- is a problem because it competes with the native California horn snail critical to the bay's food web. The Japanese snail also carries parasites that can infect native fish and can host a non-native anemone.

In the Bay Area, the snails only appear in two areas, both in Marin: Tomales Bay and Loch Lomond. In Tomales Bay, the battle is lost for now; there are too many.

"We think we have a fighting chance here in the marina to stop these snails because they have not become

widespread," Zabin said. "We are getting the bigger ones, and that's good news because the biggest snails lay the most eggs. Over time, we hope the population will crash."

If the snail's population grows, it could alter the mud flat ecosystem by creating a hard layer of dead shells that prevents shorebirds and other species from foraging.

"They can turn a mud flat into a gravel pit, the gravel being the shells," Zabin said.

The arrival of the snails dates back decades. As the aquaculture industry grew in Marin in the early 20th century, oysters were brought from Japan. With the oysters came mud and other species, including the snail, which ended up in Tomales Bay. Biologists theorize that, over the years, the snail hitched rides on the anchors of recreation boats and made it from Tomales Bay to Loch Lomond.

The Smithsonian, Marin Conservation Corps and the Bay Institute are leading the effort to stifle the invasive snail, fueled by a grant from the state's Wildlife Conservation Board.

"Look how small this one is," said Crystal Sanders of the Bay Institute, as she held up a crumb-sized snail between her blue-gloved thumb and index finger. "Once you see them and know what they look like, it goes quick. The problem is, you keep finding them."

Researchers are looking at the possibility of smothering the snails with carpeting, of using a vacuumlike device to suck them up, of dredging or of using molluscicides to kill them; but for now, the work is all by hand.

"This the first time I've done it," said Matthew Danielczyk, a Marin Conservation Corps crew supervisor, who saw his shirt and pants collect mud as the morning wore on. "It's fun. There is all kind of wildlife here. This is a great change for us; usually our work is more intense."