City Cast

A (Delicious) Threat to Colorado Waters

Peyton Garcia
Peyton Garcia
Posted on October 24
an up-close image of a rusty crayfish

Note the distinguishing dark red patches on either side of this rusty crayfish. (Wikimedia Commons)

Last month, Colorado Parks and Wildlife officials discovered rusty crayfish in Grand County’s Lake Granby. The discovery marks the first detection of the invasive species in the state in over a decade and the first ever in a reservoir that is fed by the Colorado River system, a concerning development that puts thousands of miles of water at risk. Here’s what you should know:

What Are Rusty Crayfish?

Tiny but mighty, this invasive species is known for being remarkably resilient in extreme conditions, incredibly aggressive, and nearly impossible to eradicate once established. This freshwater crustacean eats small fish, algae, water plants, and insects, imparting dramatic ripple effects on local ecosystems.

Where Did They Come From?

The rusty crayfish is native to waters in the Ohio River Valley. Biologists believe that they have been primarily introduced to Colorado lakes in the form of live bait by ignorant anglers, but perhaps also by inconspicuously hitching a ride on boating equipment.

How Do We Get Rid of Them?

With very few natural predators, the only promising method of eradication is human intervention — but even then, only to partial success. Wildlife officials will set up traps to catch what they can, but have never been successful in completely eliminating them from a Colorado lake or reservoir.

How Do You Spot a Rusty Crayfish?

It is important to know there are harmless crayfish species in Colorado. To identify a rusty crayfish, look for the distinguishing circular, dark red patch (seen in the photo above) on either side of the body just before the tail.

Can You Eat Rusty Crayfish?

Yes! In fact, they’re touted as being some of the most delicious of their kind. Just remember, live transport of the crustacean is strictly illegal. Anglers and lake-goers must pull off the heads of the crayfish before leaving the lake shore.

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