Silver Creek Mudsnail Study Completed

Mudsnails not spreading in Silver Creek, but anglers asked to continue to clean waders

PICABO, IDAHO — April 23, 2007—

Good news for Silver Creek’s famous fishery: A cold mudsnail is a dead mudsnail.

That’s the conclusion reached by a recent study completed by the University of Idaho on Silver Creek Preserve. New Zealand mudsnails, a non-native species that can crowd out native invertebrates and harm fisheries, have not spread in Silver Creek due to cold winter water temperatures.

The study was funded by The Nature Conservancy, the Idaho Department of Fish and Game and the U.S. Geological Survey Cooperative Research Unit. University of Idaho graduate student Chris James, working with Christine Moffitt of the university, conducted the two-year study.

New Zealand mudsnails were first documented in Silver Creek in September 2003, leading to concerns by Conservancy staff, landowners and anglers about their spread. In other streams, these invasive snails have crowded out native invertebrates, leading to a decline in fish populations. Cleaning stations were set up throughout the preserve so anglers could help stop the spread of the snails.

The study found that New Zealand mudsnails have not spread rapidly throughout Silver Creek. Instead, their range is isolated and associated with areas of the watershed where winter water temperatures remained above zero degrees Celsius (32 degrees Fahrenheit) in Silver Creek and Loving Creek, tributary of the stream.

According to the study published by James, “Laboratory tests confirmed that exposure of mudsnails to temperatures of zero [Celsius] for more than 72 hours resulted in 100% mortality.”

Unfortunately, in streams and rivers with warmer water temperatures, the mudsnails have taken over at alarming rates. First located along the Middle Snake River in Idaho in the mid-1980’s, the snails are now found throughout the West. In the tailwaters of the Lower Salmon Falls Dam on the Snake, mudsnails went from being common to being the dominant species in two years. In Box Canyon, near the Thousand Springs area around Hagerman, the snails were nearly as common as native snails only two months after being found.

On the Madison River in Montana, some stretches of river have more than 500,000 snails per square meter.

While Silver Creek’s limited mudsnail distribution is hopeful, Silver Creek watershed manager Trish Klahr believes that conservationists must remain vigilant.

“Climate change could tip the scales in the mudsnail’s favor,” says Klahr. “As we’ve seen so many times, non-native species often exist at low levels for a long time, until something in the ecosystem changes. Then they just take over. A slight change in Silver Creek’s water temperatures could have big impacts on the fishery.”

The Conservancy will continue to have cleaning stations for anglers located around the preserve, and hope that visitors continue to use them. The snails are tiny—ten can fit on a dime—so they can be difficult to see on waders, float tubes and other gear.

“Silver Creek may be a low risk for mudsnail spread, but anglers can move these tiny snails to other rivers where the snails can spread and thrive,” says Klahr. “It’s always a good idea to clean waders and boats to help stop spreading non-native species.”

The Nature Conservancy considers non-native, invasive species to be one of the major threats to conserving the diversity of native plants and animals worldwide. In Idaho, the Conservancy has been utilizing the latest technology to map and eradicate non-native weeds in Hells Canyon and the Owyhees. The Conservancy also practices weed control on its preserves, and engaged in public campaigns to help stop the spread of terrestrial and aquatic non-native species.

“Everyone had heard of global warming. We call this ‘global swarming,’” says Klahr. “These species cost the state millions to control, and something as tiny as a mudsnail can cause tremendous damage to Idaho’s most special places. The Nature Conservancy is committed to working with our partners to ensure that species like the New Zealand mudsnail do not spread to new waters.”

The Nature Conservancy is a leading conservation organization working around the world to protect ecologically important lands and waters for nature and people. To date, the Conservancy and its more than one million members have been responsible for the protection of more than 15 million acres in the United States and have helped preserve more than 102 million acres in Latin America, the Caribbean, Asia and the Pacific. Visit The Nature Conservancy on the Web at www.nature.org.