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National Park Service attempts to control invasive fish in the Colorado River

The Colorado River under a blue sky.
Leslie Cross

The National Park Service is attempting to control invasive fish species in the Colorado River downstream of Glen Canyon Dam.

Smallmouth bass have been slipping through the dam due to the low water levels. Last month the Park Service poisoned a slough connected to the river where the fish had been found. The effort eliminated tens of thousands of exotic carp, but almost no bass were counted. Most likely they had already escaped into the main channel.

Park Service biologist Melissa Trammell said the agency will test the effectiveness of electrofishing over the next six weeks.

"We think elimination is unlikely but we can greatly reduce their numbers in that reach, we think. That would be helpful to avoid downstream dispersal of the smallmouth bass into the rest of the Grand Canyon," Trammell said.

The Pueblo of Zuni has objected to electrofishing in the Colorado River in the past for cultural and spiritual reasons.