WHITE CITY — Two small White City ponds have the dubious distinction of being home to a large, foreign snail population that has the potential to spread throughout the Agate Desert watershed if left unchecked and leave an altered ecosystem in its wake.
These currently isolated populations of Chinese mystery snails likely got started when some nitwit emptied an aquarium into one of the two small ponds at the Jackson County Sports Park off Kershaw Road.
The snails have since exploded — a recent survey found hundreds of snails per meter — and females found there are loaded with embryos. The snails are known to carry parasites and diseases that can harm people. And the snails are just one wading dog or swimming kid away from hitchhiking to some other waterway in the Rogue River basin.
"All we know is they're not native to the watershed and they're not good," says Dan VanDyke, Rogue District fish biologist for the Oregon Department of Fish and Wildlife. "We want to get rid of this exotic species before it can get a toe-hold in this watershed."
State fish biologists and aquatic invasive species specialists plan to meet Monday with Jackson County parks officials who operate the sports park to determine how best to deal with this latest invader.
Chinese mystery snails in recent years have been discovered in a Salem pond, as well as a pond near Black Butte outside of Bend.
But the sports park ponds could be the first battleground in the state where methods are tested for killing off the offending critters, says Rick Boatner, the ODFW's aquatic invasive species coordinator based in Salem.
Options could include draining the ponds and hand-picking out the alien snails or treating the water with EPA-approved chemicals lethal to snails that wouldn't kill the ponds' natural denizens.
"We've never done an eradication in Oregon," Boatner says. "It's kind of new ground here. One way or the other, we need to get them out."
These snails are just the latest aquarium critters to find their way into the Rogue Basin's natural environment thanks to illegal dumping.
Anglers discovered large, old piranhas swimming in Expo Ponds in the late 1990s and hundreds of goldfish have been captured in netting surveys in the likes of Larson and Bear creeks.
But none of those other species have threatened the watershed like these snails, which directly compete with native snails and other nonvertebrates for food and space, Boatner says. They readily attach themselves to anything in the water, making their ability to hitchhike elsewhere a strong possibility, he says.
If you compare them to New Zealand mud snails, we don't know if they can take over like that," says Boatner, referring to an aquatic invader first discovered in the Snake River in 1987.
"Like the name implies, they're kind of a mystery," he says.
Cipangopaludina chinensis, as they are known by scientists, are somewhat commonly found in aquariums or outdoor water features because they eat algae. Yet they are banned in Oregon, one of hundreds of exotics that are illegal to possess or sell here.
They're prohibited, but we still find them in pet stores," Boatner says.
Mystery snails are large, with adult shells measuring 21/2 inches tall, and they contain a trapdoor-like feature that allows them to effectively seal themselves off against predators.
"They can stay protected a long time out of water," Boatner says.
A local angler found the snails last year and presented them to VanDyke's ODFW office in Central Point, but they were not positively identified until this summer, VanDyke says.
Boatner's invasive species team surveyed neighboring ponds and other waterways within the Whetstone Creek drainage —including the Denman Wildlife Area — but found no other snails.
Though draining the small ponds remains an option, another option Boatner wants to explore is poisoning the snails with low levels of copper sulphate, he says.
During a recent investigation of the site, crews found 166 snails per square meter, and the snails ranged from adults to juveniles, Boatner says. The second pond was too overgrown to survey, but crews found 26 adults along the banks.
"You have no problem seeing them," he says. "They're everywhere."
And they're ready to be on the move.
During the survey, a few snails took only a few minutes to attach themselves to a measuring stick in the water," Boatner says.
"Just think of a few of them attaching to a wading dog," Boatner says. "They can easily get carried to another water body."
Reach reporter Mark Freeman at 541-776-4470, or e-mail email@example.com.