When snails attack.

The New Zealand mudsnail, an aquatic, invasive species, was discovered in Oregon’s Deschutes River this September, and experts say the snail is posing a threat to Oregon’s natural habitat.


The introduction of this invasive species in Oregon threatens the natural habitat because it competes for food and space. Millions of mudsnails live on the floor of the river.


“When you get those huge population numbers and they’re carpeting the bottom of the river, there becomes a competition for space,” said Robyn Draheim, researcher at Portland State University and the Assistant Aquatic Nuisance Species Coordinator for the state of Oregon.


“In the Columbia estuary there are about 400,000 mudsnails per square meter,” Draheim said. Though these numbers are not as great in the Deschutes River, it is still a concern that the mudsnail may begin to dominate Oregon’s natural ecosystem.


Nathan Hodges, PSU alumni whose dissertation explores the urban ecology of terrestrial gastropods, has speculated on how the mudsnail could potentially damage the native ecosystem. “The endemic flora and fauna don’t have time to adapt . . . we end up with a simple ecosystem. Then it takes very little to wipe out the whole ecosystem, he said”

The rapid introduction of this non-native species could potentially debilitate and weaken the natural habitat. Draheim said that threatening the balance of the natural ecosystem, this non-native species “is going to change the nutrient cycling dynamics – the way carbon and nitrogen are processed through an aquatic system.”


Not a lot is known about mudsnails. “A species can move into a new system and it can be ten or one hundred years until we see an impact,” Draheim said. She also notes that, “You do see areas where mudsnails have come and taken over.” Because no one knows how much havoc this invasive species could potentially wreak, Draheim and her cohorts focus on preventing the introduction of non-native species, rather than on elimination.


First seen in the western United States in the Snake River in 1985, the New Zealand mudsnail is tremendously difficult to eradicate as it travels westward on the gear of boaters and anglers. “They can survive out of water for several days,” Draheim said.


It is nearly impossible to eliminate the mudsnail, an asexual invertebrate, because if even one is left behind, then the population is still able to thrive. “Because there’s no viable way of getting rid of mudsails once they’re in a system, preventing new introductions is the key,” Draheim said. An advocate of Oregon’s natural ecosystem, Draheim emphasizes the need for boaters to thoroughly clean their gear. She urged the Portland State community to become aware of the threat posed by non-native species.


“Anyone at Portland State who boats, kayaks or fishes can help prevent the introduction of mudsnails or other invasive species.”

Oregonians should especially beware of non-native species as they could potentially harm Oregon’s most prized amenity: fish. Fish don’t receive any substantial nutrition from the miniscule snail. In fact, there have been cases where mudsnails have survived in the gut of fish.


“[Mudsnails] pass through the intestinal tracts of fish and get out unscathed,” Hodges said.


“Some preliminary studies that scientists have found are that fish who eat mudsnails either lose weight or don’t gain weight,” Draheim said. Fish can’t eat them, but they are forced to share their natural habitat, competing with the mudsnail for food.


Aside from potentially starving Oregon’s natural fish, the mudsnail could impact Oregon economically, as well. “If you saw a decline in recreational fishing revenue, especially in the Deschutes, that would be a big concern,” Draheim said of their economic threat.


Draheim uses the mudsnail as a tool to teach people the importance of preventing the introduction of invasive, aquatic plants and animals. Other concerns to Oregon are the Zebra Mussel and the Chinese Mitten Crab, which carries a lung fluke that can be contracted by humans.