New Zealand mudsnails – a new threat to Utah’s fisheries

By Sun Advocate

By cleaning their boots, fishing equipment and boats, anglers can do a lot to help protect their favorite fishing water from the newest threat to Utah’s trout fisheries.
The threat is the New Zealand mudsnail. Although it’s only three-sixteenths of an inch long, it can develop colonies of more than 300,000 mudsnails per square yard.
These colonies compete for food and space needed by trout and other native aquatic organisms.
“The first discovery of the New Zealand mudsnail in North America was in Idaho’s Snake River, in 1987,” said Don Archer, special aquatic projects coordinator for the Division of Wildlife Resources. “Since then it has spread to several premier trout streams, including the Yellowstone and Madison rivers.”
Mudsnails were found in Utah in 2001, when snails were discovered in the Green River, below Flaming Gorge dam. Since then, they’ve been found in eight different watersheds in Utah.
“All New Zealand mudsnails are females and reproduce asexually, which means only one snail is required to establish a new colony,” Archer said. “They’re capable of producing several broods of young each year and are very effective at colonizing new waters.”
According to Archer, in some locations, mudsnails compose more than 95 percent of the biomass.
“They dominate these areas and because they pass through the digestive system of trout unharmed, they provide little or no food resources to fish,” he added.
New Zealand mudsnails also have a hard shell, with a protective operculum that closes the shell when the snail encounters adverse conditions. This makes them very hardy.
Their small size also makes it easy for snails to be inadvertently moved from water to water on angler’s boots, boats or other gear.
“Mudsnails can easily become lodged in the felt soles and lacings of wading shoes,” Archer said. “Anglers also spread mudsnails when they discard the entrails of cleaned fish into the water they’ve been fishing or when they don’t clean their boats thoroughly.”
Archer said anglers can avoid carrying mudnsails from water to water by thoroughly cleaning, drying or exposing their gear to freezing temperatures or hot water.
Research has shown that the snails are very vulnerable to freezing and high temperatures at low humidities.
“Wash your equipment in water that’s in excess of 140 degrees F. and allow it to dry for a couple of hours, or freeze your gear and keep it frozen for at least eight hours,” he instructed. “Either method will destroy any mudsnails that are on your gear.”
For more information, visit the DWR website at www.wildlife.utah.gov