How to avoid spreading invasive New Zealand mudsnails in Arizona waterways

PHOENIX — It’s almost time for water sports to pick back up in Arizona as spring is approaching after a rainy winter.

More boats and fishing equipment in the water raises the risk of spreading an invasive snail that impacts native species.

The New Zealand mudsnail is only 4-6 millimeters in length but can out-compete and replace populations of Arizona snails that serve as critical food sources for local fauna.

“More common pond snails and ramshorn snails are a big part of the food base for many fish, amphibians and waterfowl.” Arizona Game and Fish Department Aquatic Invasive Species Coordinator Kate Dukette told KTAR News 92.3 FM in an email.

“Pond snails and ramshorn snails occur in many of our rivers, streams, reservoirs and ponds — areas that the New Zealand mudsnail can invade and establish robust populations. Mudsnails aren’t as nutritious as the other freshwater snails. They are like junk food to foraging fish, frogs, toads and ducks.”

New Zealand mudsnails have rapidly spread throughout the United States since the 1980s and were first detected in Arizona at Lees Ferry in 2002. One snail can begin a new population, as offspring are asexually reproduced that are genetically identical. Mature females can birth up to 230 new snails every year.

According to the U.S. Geological Survey, the invaders have been observed in the Grand Canyon, Lower Lake Powell, Lower Little Colorado, Lower Salt, Lower Verde and Upper Verde watersheds.

“They have spread throughout the U.S. through gear used by anglers, boats, equipment or shoes that have come in contact with infested areas,” Dukette said. “New Zealand mudsnails are small enough that it is easy to overlook them. Anyone who comes in contact with an infested area has the potential to spread the snail.”

Dukette instructed anglers on impacted waters to clean and dry gear between each use, removing mud or plants that snails could ride within.

Strategies for ensuring surviving snails don’t latch on include freezing one’s waders or boots overnight, drying equipment completely for seven days in the warmer months (May-October) and 18 days when it gets cooler (November-April), spraying gear with hot water (140 degrees) for 10 minutes or submerging gear in a quaternary ammonia-based institutional cleaner for 20 minutes.

The cleaner would need to be disposed of away from any body of water.

For watercraft, she suggested wiping boats to get rid of any vegetation, animals, sand or mud; draining any water and completing the same dry time that applied to equipment. If a boat was on affected waters for a least six days, an AZGFD inspection is required to determine if decontamination is necessary.

The snails have elongated shells with 5-8 whorls that vary in color from gray to dark brown.

Removing an established colony of New Zealand mudsnails without impacting native populations is not possible with any known methods, according to the National Park Service.