Thursday November 18, 2021

The Durango Herald

In the 1990s, rainbow trout in Colorado died. A lot of them. Millions of them.

Whirling disease, an imported aquatic disease first discovered in Germany in 1893, left young trout swimming in circles. Nearly entire generations of rainbow trout died with kinks in their tails, catastrophic deformities from a nearly invisible parasite.

The Colorado River in Grand County lost 98% of its wild rainbow trout population.

In other river systems, the devastation wasn’t as bad, but the disease still took its toll.

The rainbow trout population in the Lower Gunnison River from Delta to Grand Junction, crashed from 2,000 adults per mile in the 1980s and early ’90s to 300 per mile by 2000.

That density dipped to about 170 adults per mile in 2014, said Eric Gardunio, an area aquatic biologist with Colorado Parks and Wildlife in Montrose.


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