California DFG vs. New Zealand Mud Snails

Article Archives/California DFG vs. New Zealand Mud Snails

USSFN: 2/22/04 - The California Department of Fish and Game (DFG) urges anglers throughout California to guard against the unintentional spread of the non-native New Zealand Mud Snails (NZMS). Discovery of NZMS has forced the emergency 120-day closure of Putah Creek in Yolo County to allow studies on the infestation and the best course of action.

In late December 2003, the snails were also discovered in the Mokelumme River, another Central Valley waterway that flows from the Sierra Nevada south of Sacramento. DFG announced the discovery after work crews with the East Bay Municipal Utilities District found the snails on equipment downstream from Camanche Reservoir, east of Lodi. Since 2000, the snails have also been found on the Owens River and Hot Creek in the Eastern Sierra.

“It is important for anyone who fishes in California or works in our waterways to take precautions to not transport the NZMS,” said Ed Pert, Chief, DFG Inland Fisheries Division. “A major factor in the spread of the NZMS is a lack of awareness by anglers and others in contact with waters infested with NZMS. These snails can survive out of water on wading and fishing gear for extended periods.”

Pert said mud snails can survive up to 25 days if they are in a moist environment, such as inside waders, on muddy wader boots, in live wells or in cooling systems at cool temperatures. DFG suggests that anglers treat their gear with at least one of the following methods to prevent spread of NZMS:

• Spray gear with Clorox Formula 409, and then scrub with stiff-bristled brush to remove all visible snails. Follow the procedure with a careful inspection of waders and gear to ensure the removal of all adults. Finish with a tap water rinse. Snails frequently collect between laces and tongue of wading boots and in the boot’s felt soles.

• Freeze waders six to eight hours. It is best to leave them in the freezer overnight to ensure complete mortality.

• Drying in air temperature over 112 degrees (50 degrees Celsius) for 24 hours will eliminate all mud snails. Alternatively, place gear in water maintained at 130 degrees for five minutes. Mortality of snails varies by exposure to heat and humidity at different combinations.

• NZMS are not the only aquatic invasive species spread by anglers and boaters. Live bait and the packaging used for some forms of live bait are known to spread other invaders. In addition, invasive aquatic plants and animals are known to hitchhike on boats, their propellers, live wells, and fishing gear. Cleaning all boating equipment is crucial to reducing the impacts from non-native invasive species.

DFG biologists and field staff members who conduct studies in the infested areas have received similar instructions to guard against the spreading of NZMS, Pert said.

DFG warns that the snails in Putah Creek have been collected on the banks, well away from the water’s edge. Outdoor enthusiasts and boaters who travel within the riparian areas should also follow the guidelines.

NZMS is a very small snail with the potential of extraordinary population densities – up to approximately a million snails per square meter. Populations in New Zealand are limited naturally by native parasites and predators. In North America, however, there are no natural predators or parasites of the snail and the populations have flourished where introduced. Currently, no method of eradication has been successfully applied to large, open river systems.

Putah Creek began its 120-day closure on Dec. 26, 2003. The Fish and Game Commission ordered the emergency action, which received support from various fly-fishing clubs, to close the popular winter trout fishery from Monticello Dam downstream to, and including, Lake Solano in Yolo County. There are currently no plans to close the Mokelumne River, which is about 40 miles away from Putah Creek.

Contacts: Ed Pert, Chief, DFG Inland Fisheries Division, (916) 445-3616; Patrick Foy, DFG Information Officer, (916) 358-2938; Steve Martarano, DFG Office of Public Affairs, (916) 654-5866

Source: California Department of Fish and Game