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TROUT OPENER -- mud snail -- Jim Matthews-ons 24apr02
New Zealand mud snail expanding range in Sierra; fisheries could be harmed
The most serious threat to trout fisheries in the Western United States -- potentially far worse than whirling disease -- is being spread rapidly by those who generally fight to save fisheries.
The New Zealand mud snail is invading the West's premier trout waters at a rapid pace, most likely being carried from water to water in the waders and gear of traveling anglers. Once in its new home, the tiny snail reproduces so rapidly and prolifically, it becomes the primary life-form in streams and lakes, almost completely displacing all other aquatic invertebrates.
With trout season opening in the Sierra Nevada this weekend, biologists with the Department of Fish and Game are sounding the alarm for the second year in a row. In just one short season, the small snail has found its way into more Eastern Sierra waters, most likely the result of hitching rides with wader-clad anglers who visit the Sierra's best waters over the course of a weekend.
The snail was first discovered at one location in the upper Owens River in 1999. Since then, it has been found in the canals around Bishop, in the Wild Trout stretch of the lower Owens, and further downstream near popular fishing locations.
"It looks to me like its centered on areas of high recreational use," said Dawne Becker, an associate fishery biologist with the DFG in Bishop. "We only had a couple of sites in the Owens River last year. This year, we have really high densities of the snail at Five Bridges Road and in the Wild Trout stretch."
By where the snail is appearing, it is almost certain that anglers are inadvertently spreading the snail to their favorite waters.
The New Zealand mud snail has been in the Western United States since at least 1987, when it was first found in the middle sections of the Snake River in Idaho. It had found its way to the Madison River by 1989, and by 1994, it was throughout the greater Yellowstone ecosystem -- infecting famous rivers like the Firehole and Gibbon. By 1997, it had spread to over 300 miles of the Snake River, moving both upstream and down.
The small snail, which grows no bigger than 12mm, or about 1/2-inch, with most being 3.5mm to 5mm, can reproduce prolifically. Most importantly, it rapidly displaces other organisms. In the upper Madison River, it has already been found at densities of 300,000 to 1,000,000 snails in a square meter of stream bottom, and it comprises up to 95 percent of the total invertebrates at many sites.
"It is completely changing trout stream ecosystems," said David Richards, a research ecologist with EcoAnalysists in Bozeman, Mt., and a PhD candidate at Montana State University. "It has the potential to destroy some of our premier trout fisheries. My personal feeling is that spring creek and highly productive trout streams will be the most highly impacted."
Richards said that many sections of the Madison and Firehole have already seen their aquatic insect populations drop by 50 to 75 percent.
In California, the New Zealand mud snail could spell doom for the prolific invertebrate populations that exist now on waters like Hot Creek, the upper Owens River, Crowley Lake, and any other water where they are introduced. It is the invertebrates that make healthy trout populations possible at these waters and they are being displaced by the snail. Because the mud snail has almost no nutritional value to trout, fish populations are almost certain to crash. Even if the trout eat the mud snails, the snail can close its operculum, the door to its snail shell, and survive passage through the fish's gut. They get no nutritional value from the snail.
"There are a lot of indirect impacts to the fishery," said the DFG's Becker. But she warned there are no ways known to get rid of the snail once its in a fishery. "How are we going to handle this thing? Our biggest effort has to be in training people how not to be vectors -- to stop the spread and contain the population to where it exists now."
The mud snail can survive up to 25 days out of water in a moist environment (the felt in waders, a damp boot sole, etc.), and a single snail can start a new population. So fishery managers are trying to stop the spread of the snail by asking anglers to make sure they clean and thoroughly dry their waders and other gear that might carry a snail from water to the next -- especially when they fish waters known to have mud snails.
Because the mud snail is such a recent introduction to this country, its full impacts on trout fisheries is yet to be known, but many biologists are fearful it may have catastrophic consequences.
SIDEBAR: HOW TO NOT TRANSPORT MUD SNAILS -- matthews-ons 24apr02
How to prevent the spread of New Zealand mud snails
Anglers can help prevent the spread of the New Zealand mud snails by following these tips offered by the Department of Fish and Game:
-- Rinse all fishing equipment -- waders, wading shoes, socks, and any other fishing gear or clothing -- in water at least 115 degrees for no less than 15 seconds. This will kill New Zealand mud snails.
-- If a hot rinse in not available, completely dry all equipment and brush off all debris. Mud snails can survive up to 25 days in a moist environment and young snails can be as small as a grain of sand.
-- Expose equipment to extremely hot temperatures or cold temperatures.
-- Do not transport fish to other waters before cleaning them and discard guts in closed trash containers or bury them. Mud snails can live in a trout's gut and can be transported in this way.
-- If you plan to fish a number of waters in an area, visit the sites known to have New Zealand mud snails last.
-- Pets and pack stock wading through infected waters can pick up snails and transport them in wet hair or fur.
New Zealand mud snail expanding range in Sierra; fisheries could be harmed
The most serious threat to trout fisheries in the Western United States -- potentially far worse than whirling disease -- is being spread rapidly by those who generally fight to save fisheries.
The New Zealand mud snail is invading the West's premier trout waters at a rapid pace, most likely being carried from water to water in the waders and gear of traveling anglers. Once in its new home, the tiny snail reproduces so rapidly and prolifically, it becomes the primary life-form in streams and lakes, almost completely displacing all other aquatic invertebrates.
With trout season opening in the Sierra Nevada this weekend, biologists with the Department of Fish and Game are sounding the alarm for the second year in a row. In just one short season, the small snail has found its way into more Eastern Sierra waters, most likely the result of hitching rides with wader-clad anglers who visit the Sierra's best waters over the course of a weekend.
The snail was first discovered at one location in the upper Owens River in 1999. Since then, it has been found in the canals around Bishop, in the Wild Trout stretch of the lower Owens, and further downstream near popular fishing locations.
"It looks to me like its centered on areas of high recreational use," said Dawne Becker, an associate fishery biologist with the DFG in Bishop. "We only had a couple of sites in the Owens River last year. This year, we have really high densities of the snail at Five Bridges Road and in the Wild Trout stretch."
By where the snail is appearing, it is almost certain that anglers are inadvertently spreading the snail to their favorite waters.
The New Zealand mud snail has been in the Western United States since at least 1987, when it was first found in the middle sections of the Snake River in Idaho. It had found its way to the Madison River by 1989, and by 1994, it was throughout the greater Yellowstone ecosystem -- infecting famous rivers like the Firehole and Gibbon. By 1997, it had spread to over 300 miles of the Snake River, moving both upstream and down.
The small snail, which grows no bigger than 12mm, or about 1/2-inch, with most being 3.5mm to 5mm, can reproduce prolifically. Most importantly, it rapidly displaces other organisms. In the upper Madison River, it has already been found at densities of 300,000 to 1,000,000 snails in a square meter of stream bottom, and it comprises up to 95 percent of the total invertebrates at many sites.
"It is completely changing trout stream ecosystems," said David Richards, a research ecologist with EcoAnalysists in Bozeman, Mt., and a PhD candidate at Montana State University. "It has the potential to destroy some of our premier trout fisheries. My personal feeling is that spring creek and highly productive trout streams will be the most highly impacted."
Richards said that many sections of the Madison and Firehole have already seen their aquatic insect populations drop by 50 to 75 percent.
In California, the New Zealand mud snail could spell doom for the prolific invertebrate populations that exist now on waters like Hot Creek, the upper Owens River, Crowley Lake, and any other water where they are introduced. It is the invertebrates that make healthy trout populations possible at these waters and they are being displaced by the snail. Because the mud snail has almost no nutritional value to trout, fish populations are almost certain to crash. Even if the trout eat the mud snails, the snail can close its operculum, the door to its snail shell, and survive passage through the fish's gut. They get no nutritional value from the snail.
"There are a lot of indirect impacts to the fishery," said the DFG's Becker. But she warned there are no ways known to get rid of the snail once its in a fishery. "How are we going to handle this thing? Our biggest effort has to be in training people how not to be vectors -- to stop the spread and contain the population to where it exists now."
The mud snail can survive up to 25 days out of water in a moist environment (the felt in waders, a damp boot sole, etc.), and a single snail can start a new population. So fishery managers are trying to stop the spread of the snail by asking anglers to make sure they clean and thoroughly dry their waders and other gear that might carry a snail from water to the next -- especially when they fish waters known to have mud snails.
Because the mud snail is such a recent introduction to this country, its full impacts on trout fisheries is yet to be known, but many biologists are fearful it may have catastrophic consequences.
SIDEBAR: HOW TO NOT TRANSPORT MUD SNAILS -- matthews-ons 24apr02
How to prevent the spread of New Zealand mud snails
Anglers can help prevent the spread of the New Zealand mud snails by following these tips offered by the Department of Fish and Game:
-- Rinse all fishing equipment -- waders, wading shoes, socks, and any other fishing gear or clothing -- in water at least 115 degrees for no less than 15 seconds. This will kill New Zealand mud snails.
-- If a hot rinse in not available, completely dry all equipment and brush off all debris. Mud snails can survive up to 25 days in a moist environment and young snails can be as small as a grain of sand.
-- Expose equipment to extremely hot temperatures or cold temperatures.
-- Do not transport fish to other waters before cleaning them and discard guts in closed trash containers or bury them. Mud snails can live in a trout's gut and can be transported in this way.
-- If you plan to fish a number of waters in an area, visit the sites known to have New Zealand mud snails last.
-- Pets and pack stock wading through infected waters can pick up snails and transport them in wet hair or fur.
