Invasive species threatening local waters
February 22, 2008
The California Department of Fish and Game (DFG) recently released a press release regarding its concern about the New Zealand Mud Snail (NZMS) ” an invasive species that was first found in the Owens River in Mono County in 2000.
Since that time the tiny snails have been confirmed in numerous other waters within California. According to Susan R. Ellis, DFG Invasive Species Coordinator, “New Zealand mud snails are just one of the many non-native invasive species that are impacting our natural resources.”
The DFG is appealing to the general public 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.
NZMS reproduce rapidly and can crowd out native insects that aquatic wildlife depend on for their survival. The snails have now been found in the following waters and county since their discovery in 2000: Hot Creek (Mono); Bishop Creek Canal (Inyo); Lone Pine Creek (Inyo); Media 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); 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).
Most recently, it has been confirmed in Lake Shasta as well.
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It is believed that NZMS spread to new river systems primarily by humans, although it is also possible that wildlife plays a role. Anyone who frequents lakes, rivers and streams can inadvertently move mud snails to new locations and therefore should clean their gear. For example, the snails can attach to debris and mud left on waders and survive for weeks in these moist conditions. When an angler or anyone else who has contaminated equipment visits a new stream, the snails can deposit there.
The snails form colonies that disrupt the base of the food chain by consuming algae and competing with native bottom-dwelling invertebrates. A population decline of invertebrates (small aquatic insects, or trout food) can follow the introduction of NZMS, which reduces fish forage. With a decrease in food availability, fish populations can decline as well.
NZMS can grow as large as one-quarter inch but are often much smaller and are parthenogenic or able to start a population with only one snail. 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.
It is believed that population in New Zealand is 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 that they can eradicated once established.
Here are some steps that the DFG recommends taking if you have been along a stream that is known to have NZMS:
– Have extra waders and boots for use in infested waters only. Store them separately.
– After leaving the water, inspect waders, boots, float tubes, boats and trailers, dogs and any gear used in the water.
– Remove viable snails with a stiff brush and follow with a rinsing.
– If possible, freeze or completely dry out wet gear before reuse.
– Never transport live fish or other aquatic animals or plants from one body of water to another.
Quagga and Zebra mussels that first invaded North America in the Great Lakes region have also been getting a lot of coverage in the media lately. Quagga mussels were found in the Colorado River in early 2007 and later in several bodies of water in San Diego and Riverside counties. Both of these species of mussels, which are native to Caspian Sea and Black Sea watersheds, are of great concern because of their ability to cause severe damage to the natural environment as well as to power plants and water supply intakes.
Invasive species are having a huge impact on our resources nationwide. Please exercise great care when you are out enjoying the great outdoors and be aware of accidentally transporting these unwanted visitors.
The threat to Lake Tahoe waters remains real with at least some plans put in place to prevent the invasive mussels from making their way here.
An agricultural inspection station at Interstate 80 in Truckee and four others now looks for quagga and zebra mussels on boats coming into the state. This was made possible through a $2.5 million grant from the California Department of Food and Agriculture.
The Tahoe Resource Conservation District is hiring watercraft inspectors for the upcoming boating season to patrol Lake Tahoe waters. Also, the Tahoe Regional Planning Agency has looked at buying a portable boat-wash station, which may be up and running by the end of July.
Bruce Ajari is a Truckee resident and regular fishing columnist for the Sierra Sun and other area newspapers.