12/6/15
An invasive species of snail that is able to self-reproduce by the hundreds and outcompete native species has been discovered for the first time in Humboldt State University’s College Creek, and there is no known method to stop its exponential spread.
The new habitat between the HSU campus dorms and soccer field now provides the snails a foothold in the Arcata area to spread to other streams and watersheds like Jacoby Creek and the Mad River, HSU Fisheries Biology Assistant Professor Darren Ward said.
“There’s nothing to really stop them moving through that and moving downstream,” he said. “... That’s the best thing we can do at this point, is to keep them from spreading around even more.”
But stopping the spread is no easy feat. Measuring in at only 5 millimeters — or about a fifth of an inch — and living in wet areas like streams and rivers, New Zealand mudsnails can easily get wedged in the sole of a fishing boot or make their way into gear, boats and even hitch a ride on shoelaces, according to California Department of Fish and Wildlife Aquatic Invasive Species Coordinator L. Breck McAlexander in Redding.
The snails have already established populations in Humboldt Lagoons State Park since at least 2008 and have also been found on the Klamath and Smith rivers and Redwood Creek. While he did not know exactly how the snails got into College Creek, McAlexander had his guesses.
“Humboldt State is like a mecca for fishermen,” McAlexander said. “That makes it an easy place to get those mudsnails established. Probably, these things are not going to go away. It’s just a matter to limit their spread in the meantime.”
Arcata Environmental Services Director Mark Andre said the snails have the potential to spread from College Creek. The creek drains into Campbell Creek and eventually leads to Gannon Slough, which can intermingle with Jacoby Creek during flood seasons.
“If it’s isolated we want to help keep it that way,” Andre said.
Native to freshwater streams and lakes in New Zealand, the snails were first discovered in the U.S. at the Snake River in Idaho in 1987 and later discovered in the Owens River in southeastern California in 2000. The snails have now spread to more than 15 states across the country, according to the U.S. Geological Survey.
What makes the mudsnails so successful is their ability to self-reproduce, Ward said. Females produce their young live rather than in eggs and have up to 230 offspring per year. One snail and its offspring are able to produce up to an estimated 2.7 billion snails within four years, according to the Department of Fish and Wildlife. The young already have developing embryos when they’re born and can reach maturity in about three to four months, Ward said.
How these population booms effect local waters is hard to measure, McAlexander said.
“The most obvious observation you can make is when these snails get established, they create explosive populations and the sheer numbers you can see makes you realize that they’re going to have an impact on the ecology,” he said.
The snails can also outcompete native marine invertebrates for food and space, which in turn can reduce the amount and diversity of food available to predators like fish, McAlexander said. He added that the mudsnails are also a poor food substitute for some fish.
Feeding trials conducted on rainbow trout that were only fed mudsnails found that 54 percent of mudsnails they ate passed through their digestive systems and came out alive, according to the Department of Fish and Wildlife. The tested fish lost up to a half-percent of their initial body weight every day, “which is nearly equal to the impact of starvation,” according to the department.
McAlexander said this could cause issues for fisheries, although no major economic impacts have been associated with the mudsnails’ spread.
Andre said the city is monitoring the issue and will follow the state’s protocol to prevent any “ecological chain reactions” caused by the snails. He said they are training the city’s utilities and street crews about the issue and how to prevent the spread.
Methods on how to prevent the spread of New Zealand mudsnails can be found on the California Department of Fish and Wildlife’s website at https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=22574&;inline.
