COLORADO PARKS & WILDLIFE

CPW announces discovery of Rusty Crayfish in Lake Granby

GRAND LAKE, Colo. - Colorado Parks and Wildlife announces the discovery of rusty crayfish in Lake Granby, south of Grand Lake, Colorado.  

Multiple crayfish were found at Lake Granby during routine Aquatic Nuisance Species (ANS) sampling by CPW’s ANS Sampling and Monitoring team near Sunset Point campground, on Aug. 17. Samples were collected by the tam, preliminary species identification was performed at CPW’s ANS laboratory and suspect specimens were sent to Pisces Molecular in Boulder for genetics testing, where the samples were confirmed to be rusty crayfish on Aug. 31. 

CPW’s ANS Sampling and Monitoring team and area aquatic biologists set multiple crayfish traps around Lake Granby and other waters in close proximity to determine the extent of the rusty crayfish population in the area during the week of Sept. 11. Sampling traps were left overnight before being collected. Crayfish traps collected from the surrounding lakes did not contain crayfish; however, two traps from Lake Granby did contain rusty crayfish. A trap was set below the dam on the Colorado River in addition to the lakes. No crayfish were found in this trap upon removal.

“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. “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.” 

Rusty crayfish were first discovered in Yampa River and Catamount Reservoir in 2009.They are a la​rger, more aggressive freshwater crayfish, native to the Ohio River Basin. The rusty patches on either side of their body can sometimes identify them. They are believed to have been illegally introduced to Colorado by anglers ​​as bait.

The public is reminded by following these simple steps, they can prevent the introduction and spread of invasive species in Colorado.

• 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. 

“When you follow these simple steps, you’re not just protecting the lake or river you’re recreating in, you're protecting every water body in Colorado,” said Walters.

Crayfish of any species are not native west of the continental divide. CPW reminds the public the live transportation of all crayfish from waters west of the Continental Divide is prohibited. All crayfish caught west of the Continental Divide must be immediately killed (by removing the head from the thorax) and taken into possession, or immediately returned to the water from which they were taken. 

Image 1: ANS Sampling and Monitoring team members separating and identifying crayfish from Lake Granby during trapping efforts the week of Sept. 11. 

Image 2: Empty crayfish traps used in trapping efforts at multiple sites at Lake Granby, and additional bodies of water nearby.