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DOW invasive species sampling technicians collected several specimens of rusty crayfish during routine shoreline surveys in late August and early September. Subsequent testing performed at the Aquatic Animal Health Lab in Brush in September identified the specimens as rusty crayfish. The Illinois State Museum confirmed the finding on Oct. 14.
"Rusty crayfish are a tenacious invasive species that have the potential to impact streams and lakes," said Greg Gerlich, the DOW's aquatic section manager. "We need the public's help to prevent this noxious pest from being moved to other places across the state."
An aggressive and invasive fresh-water crustacean, the rusty crayfish (Orconectes rusticus) has large claws and out-competes native species for food and habitat. Rusty crayfish will displace native crayfish from secure areas, making them more vulnerable to predation. They can clear large areas of aquatic plants, reducing habitat for invertebrates and shelter for small fish. They have a higher metabolic rate and appetite than other crayfish species and attain higher population densities. One study suggested that rusty crayfish might consume twice as much food as a similar-sized northern crayfish, which is native to Colorado's East Slope. No crayfish are native to the West Slope of Colorado.
Native to the Ohio River Basin, the rusty crayfish has been spread by human activity such as its use as live bait by fishermen and the release of live specimens purchased from biological supply houses by educational facilities. It is now known to infest waters throughout the northeast United States and parts of southern Canada. In recent years, the crayfish has been found further west, inhabiting waters in New Mexico and Colorado. Crayfish, also known as "crawdads," are also harvested as a food item, increasing the likelihood of their transport and introduction to other waters.
The discovery of rusty crayfish at Sanchez Reservoir marks the third location where the species has been detected in Colorado. State wildlife officials first discovered the species in 2009 in the Yampa River near Steamboat Springs--prompting a basin-wide emergency prohibition on the take of live crayfish.
To prevent the spread of rusty crayfish beyond Sanchez Reservoir, Remington signed an emergency administrative closure which prohibits the removal of any live crayfish from the impoundment. Anglers collecting crayfish must either return them to the reservoir alive or immediately kill the crayfish by separating the crayfish's tail from the body, or thorax. Even crayfish harvested for human consumption must be killed by separating the edible tail from the body before leaving the reservoir.
Colorado law prohibits the use of rusty crayfish as bait anywhere in the state. However, identification of rusty crayfish is extremely difficult and requires laboratory analysis of mature males. Because of the identification challenge, it is unlikely that anglers will be able to identify rusty crayfish from other crayfish found in the reservoir. As a result, a complete prohibition on the transport of any crayfish is warranted.
Anglers can help stop the spread of rusty crayfish and other invasive species by purchasing live bait from reputable, licensed dealers and disposing of unused bait into appropriate waste receptacles. Anglers should never transfer live crayfish or other live bait from one water body to another.
DOW aquatic biologists and invasive species specialists will continue to inventory Colorado waters for the presence of rusty crayfish and other aquatic invasive species. The DOW is currently monitoring more than 200 standing and flowing waters as part of a statewide initiative to stop the spread and introduction of harmful invasive species.
For more information about the rusty crayfish and links to the emergency orders closing Sanchez Reservoir and the Yampa Basin to live crayfish collection, please visit the Division of Wildlife's website: http://wildlife.state.co.us/WildlifeSpecies/Profiles/InvasiveSpecies/RustyCrayfish.htm
To submit questions or comments about rusty crayfish or this closure, please contact Elizabeth Brown, Division of Wildlife invasive species coordinator, at (303) 291-7362, or by e-mail at Elizabeth.firstname.lastname@example.org
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