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'Invasive' rusty crayfish discovered at Lake Granby

rusty crayfish lake granby.png
Posted at 5:24 PM, Sep 19, 2023

DENVER — Colorado Parks and Wildlife on Monday announced the discovery of the invasive rusty crayfish in a previously undetected area of Colorado.

CPW said rusty crayfish were discovered during routine sampling at Lake Granby, which is south of Grand Lake.

Described as more aggressive and larger than freshwater species, rusty crayfish are an aquatic nuisance species (ANS) first discovered in Colorado in 2009 in Yampa river and Catamount Reservoir, according to CPW.

Rusty crayfish eat aquatic vegetation andcan damage the natural underwater habitat “important for fish spawning, cover and food,” according to the CPW website.

“While this is not the first time we have found rusty crayfish west of the divide here in Colorado, it is the first detection in the Upper Colorado River basin,” said Robert Walters, CPW’s Invasive Species Program Manager in a news release. “While finding any invasive species is detrimental to our state’s aquatic ecosystems, finding rusty crayfish in Lake Granby, which feeds into the Colorado River, poses an even greater threat to the entire Colorado River Basin.”

CPW said it has been removing adult rusty crayfish when found in an attempt to limit reproduction and limit impact to native communities.

It is believed rusty crayfish were first introduced in Colorado illegally by anglers as bait, according to CPW. To prevent the spread of the species, CPW recommended these tips:

  • Use only bait that is legal in Colorado! Never bring in live aquatic bait from another state.
  • Do not throw unused bait of any kind, back in the water alive.
  • Clean, Drain, and Dry your gear and water craft before heading to the next body of water.
  • Do not dispose of pets or unwanted aquarium plants or animals in natural systems.

All species of crayfish are not native west of the continental divide, CPW said, and transporting live crayfish from waters west of the divide is not allowed.