Disease-Resistant Strain Of Rainbow Trout Is Helping The Species Rebound

Starting in the late 1980s, rainbow trout in Colorado began dying off because of a parasite that causes whirling disease. By 1997, wild rainbows in the state had all but vanished.

The disease is caused by a water-borne parasite that infects young trout and some species of salmon, causing deformities of the skull and spinal column. The infected fish swim in circles, hence the name whirling disease. Ultimately, it leads to death.

But now, thanks to efforts from Colorado Parks and Wildlife (CPW), the fish — which is not native to Colorado but is popular with anglers and conservationists alike — could be on the rebound.