The California Department of Fish & Game is requesting assistance from the public in slowing the spread of New Zealand mud snails (NZMS).

The tiny invasive aquatic snails were confirmed last month to live in Lake Shasta, and previously have been discovered in numerous bodies of water throughout the state.

NZMS have the potential of extraordinary population densities — up to nearly one million snails per square meter and comprising up to 95 percent of the invertebrate biomass of a river.

They can grow as large as one-quarter inch, but are often much smaller and parthenogenic — able to start a new population with only one snail.

It is believed that populations in New Zealand are kept in check naturally by a native parasite. In North America, however, native stream communities can be altered because the snail has no natural predators or parasites and its populations have flourished where they have been introduced. It is not believed they can be eradicated once established.

Colonies of NZMS will disrupt the base of the food chain by consuming algae and competing with native bottom-dwelling invertebrates (small aquatic insects). A population decline of the native invertebrates can follow, which reduces fish forage.

With a decrease in food availability, fish populations can decline as well.

Fish cannot digest the NZMS. If eaten, they will pass through the fish’s system undigested.

NZMS were first discovered in California eight years ago in Mono County’s Owens River.

Other bodies of water (and the counties) in which they have been found include: Hot Creek (Mono), Bishop Creek Canal (Inyo), Lone Pine Creek (Inyo), Medea Creek (Los Angeles), Lindero Creek (Los Angeles), Malibu Creek (Los Angeles), Solstice Creek (Los Angeles), Segunda Descheca Creek (Orange), Trabuco Creek (Orange), Piru Creek (Ventura), Lower Putah Creek (Yolo), Lower Calaveras River (Calaveras/San Joaquin), Mormon Slough (San Joaquin), Lower Mokelumne River (San Joaquin/Sacramento), American River (Sacramento), Rush Creek (Marin), Lower Napa River (Napa), San Lorenzo River (Santa Cruz), West Antioch Creek (Contra Costa), and Alameda Creek (Alameda).

It is believed that NZMS spread to new river systems primarily by humans, although it also is possible that wildlife plays a role. Recreationists such as anglers, boaters, researchers and others who frequent lakes, rivers and streams can inadvertently move mud snails to new locations and therefore should carefully clean their gear.

The snails can attach to debris and mud left on waders and survive for weeks in these moist conditions. When an angler visits a new stream, the snails can deposit there and begin to reproduce almost immediately.

To help prevent further spread of the snails, anglers and others who frequent California waters are asked to thoroughly clean all gear that comes in contact with the water prior to moving to another location.

In addition, individuals who are visiting state fish hatcheries should be careful to remove waders that have been in contact with affected waters before entering hatchery grounds.

Following these steps will also help prevent the spread of these dangerous creatures:

• Have extra waders and boots for use in infested waters only. Store them separately.

• After leaving the water inspect waders, boots, float tubes, boats, trailers, dogs and any gear used in the water.

• Remove visible snails with a stiff brush and follow with a rinsing.

• If possible, freeze or completely dry out wet gear before re-use.

• Never transport live fish or other aquatic animals or plants from one body of water to another.

For more information on NZMS and where they have been detected, visit the DFG Web site at www.dfg.ca.gov/invasives/mudsnail.

Guy Carl is a CPA and partner with Brotemarkle, Davis & Co. Accountants and Advisors in St. Helena.

Contact Guy at GC.outdoors@sbcglobal.net.