Another invasive species has made its way to Skagit County, this time in the waters of Big Indian Slough off of Padilla Bay south of Bay View.

New Zealand mudsnails are tiny, spiral-shelled creatures that thrive in lakes, rivers, streams and estuary environments where freshwater and saltwater meet.

Other invasive species found in the county range from blackberry bushes to green crabs.

While the newfound mudsnails are small — each about the size of former President Abraham Lincoln’s ear on the penny — they reproduce rapidly, creating quantities that can clog pipes or habitat used by other species.

“New Zealand mudsnails are very prolific, and they can reproduce asexually, so all it takes is one,” said Karen DuBose, Skagit County pollution identification and correction coordinator.

The state Department of Fish & Wildlife estimates a single female snail can produce 230 snails a year. At that rate, the number can reach billions within four years, starting from just one female.

The snails’ rapid population growth can threaten ecosystems on which native species rely.

Fish & Wildlife’s website states that the mudsnails eat algae that is important for insects young salmon rely on for food.

The invasive snails are also hardy. They have the ability to survive in a wide range of temperatures, can shield themselves from chemicals and have no natural predators, according to various wildlife agencies.

DuBose said Skagit County Public Works learned about the snails in Big Indian Slough in late May.

Chris McGann of the state Department of Agriculture said the snails were found by the state agency’s water quality monitoring team in September and confirmed by the state Department of Fish & Wildlife in November.

The invasive snails could have arrived attached to other wildlife or on equipment such as a boat or fishing waders.

“They’re very small and spread easily,” DuBose said. “There’s a good chance they hitched a ride on waterfowl or perhaps some equipment that was used in a contaminated waterway and not subsequently decontaminated.”

Since their first appearance in the United States — in 1987 in Idaho’s Snake River — the snails have spread to 20 states, largely concentrated in the Pacific Northwest and around the Great Lakes, according to the U.S. Geological Survey.

Their debut in Washington was in 2000 in the Columbia River, according to the USGS. They are now found in 17 waterways throughout the state.

The snails have also been found in neighboring counties.

They were found in Whatcom County’s Lake Padden in August 2018 and in Snohomish County’s Union Slough in 2013, according to USGS data.

“The New Zealand mudsnail has a history of becoming a pest species in many parts of the world, and its recent introduction into North American waters is cause for concern,” the federal Aquatic Nuisance Species Task Force website states.

There’s no known solution for removing the snails.

“There isn’t much we can do about them once they’re here,” DuBose said.

The main course of action is to ask those recreating in contaminated waters to thoroughly wash boats, waders and other materials.

“Learn what they (snails) look like, learn where they are, and follow decontamination procedures always, regardless if there’s a known problem in the waterway you’re in,” DuBose said. “We always recommend cleaning boots when hiking, fishing, or wading before going into another area.”

That has been the city of Bellingham’s primary strategy in its effort to keep the invasive New Zealand mudsnail confined to Lake Padden and out of nearby waterways.

“We are still working on our long-term response strategy but are doing as much outreach as possible to get the public to help us to contain the snails in Padden,” said Teagan Ward, the city of Bellingham’s aquatic invasive species program coordinator.

The city made up fliers about the snails and has staff frequently stationed at Lake Padden Park to inform visitors of the problem.

DuBose said while Skagit County has work to do on the outreach front, an added challenge here is how many waterfowl dip in and out of the contaminated slough and other local waterways each year.

— Reporter Kimberly Cauvel: 360-416-2199, kcauvel@skagitpublishing.com, Twitter: @Kimberly_SVH, Facebook.com/bykimberlycauvel

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