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The California Department of Fish and Game (DFG) recently released a press release regarding its great concern for the New Zealand Mud Snail (NZMS). It is an invasive species that was first found in the Owens River in Mono County in 2000.
Since that time the tiny invasive snails have been confirmed in numerous other waters within California. According to DFG Invasive Species Coordinator, Susan R. Ellis, “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 upon for their survival. The snails have now been found in the following waters and county since their discovery in 2000 in the Owens River: 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.
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 that 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, 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 pathogenic 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 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 that they can be 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 present:
• 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 in Europe, are of great concern because of their ability to cause severe damage to the natural environment as well as to power plants, water supply intakes, as well as other negative impacts.
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.
Bruce Ajari is a Truckee fisherman who writes columns for the Bonanza, as well as other area publications.
Since that time the tiny invasive snails have been confirmed in numerous other waters within California. According to DFG Invasive Species Coordinator, Susan R. Ellis, “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 upon for their survival. The snails have now been found in the following waters and county since their discovery in 2000 in the Owens River: 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.
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 that 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, 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 pathogenic 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 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 that they can be 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 present:
• 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 in Europe, are of great concern because of their ability to cause severe damage to the natural environment as well as to power plants, water supply intakes, as well as other negative impacts.
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.
Bruce Ajari is a Truckee fisherman who writes columns for the Bonanza, as well as other area publications.
Fishing Report
Boca - (5,220 Acre Feet) Inflow is at 138 c.f.s. and the outflow is 52 c.f.s. Boca is frozen over and there is a little water available to fish near the inlet. Fishing near the inlet has been fair at best. Take great care if you are going to make an attempt at ice fishing. Ice fishing has been fair to good. Cold temperatures have kept ice pretty consistent. Donner – Fishing has been fair. The lake has iced over, but the west end generally warms and provides some open water to fish. Shore fishermen have had fair. Night crawlers and Powerbait seem to be the main bait. Fly fishermen are catching some fish with streamers.
Lake Tahoe – At 6225.06 on Feb. 18 (Lake Level 6223.00) Fishing has been good for mackinaw. A guide is highly recommended if you are fishing for mackinaw for the first time. Toplining and shore fishing is fair. Most shore fishermen use inflated night crawlers. Lake Tahoe tributaries are closed.
Little Truckee River – (138 c.f.s.) Winter Season Regulations: Artificial Lures with barbless hooks and a zero fish limit (strictly catch-and-release). The flow is at 138 c.f.s. Small flies have been the best here although streamers have also been productive at times. Baetis and midges remain the main attraction although winter stoneflies are also an option. Zero fish may be kept and only artificial lures or flies with barbless hooks are permitted.
Prosser – (7,130 Acre Feet) Ice has formed on this lake as well. See the Boca report since conditions are similar at Prosser.
Stampede – (147,000 Acre Feet) Stampede fishing has been fair. Shore fishermen have found action fair. Most are using night crawlers or Powerbait. Boat action has been fair to good. Fly fishermen are using a combination of nymphs and streamers with fair success.
Truckee River – (175 c.f.s from Tahoe City to 297 c.f.s. at Boca Bridge) – Winter Season Regulations: Artificial Lures with barbless hooks and a zero fish limit (strictly catch-and-release). Consult the regulation book for details. The river is fishing well. The upper section from Tahoe City to River Ranch flow is 175 c.f.s. and is now closed all the way down to where Trout Creek enters the Truckee River just east of the town of Truckee. Fishing is now permitted from Trout Creek to the Nevada state line. Zero fish may be kept and only artificial lures or flies with barbless hooks are permitted. Nymphs or streamers are your best bet for the best chance at mid-day action. Baetis and midges have also come off in good numbers so small nymphs and dries to imitate them can be productive.
Other Waters – Frenchman Lake north of Truckee has iced over. Davis Lake has been treated and is now open to ice fishing. Pyramid Lake on the Paiute Indian Reservation northeast of Reno is open. Fishing has slowed. Water temperatures are in the low forties. Shore fishing has been fair and quite spotty. Fishing should slowly pick-up in the coming months.
