The “catastrophic” flash flooding and mudslides that occurred at the Black Hollow Creek confluence with the Poudre River last summer had deadly consequences for the area’s fish population and the Poudre River State Fish Hatchery, according to a report from Colorado Parks and Wildlife (CPW). This event added to the long list of impacts to the Cameron Peak fire.

“The plume of sediment and debris that moved downstream from that event led to fatal conditions in the river for fish due to heavy sediment loads preventing fish from exchanging oxygen across their gills, leading to the fish suffocating,” said CPW Aquatic Biologist Kyle Battige. 

A true estimate of the loss was not immediately available due to high sediment levels in the water, CPW reported. CPW biologists and technicians conducted a 10-day survey of the river last fall to identify the impact. 

“No fish, outside of a single brown trout that had migrated downstream between the dates of the debris flow event and sampling event, were captured during sampling within stations from one to 16 miles downstream of Black Hollow Creek confluence, suggesting a complete loss of the fishery within that reach,” Battige said.

“It was not until the Stove Prairie station, 20 miles downstream, that trout were captured.”

The study determined that trout numbers were 80 percent lower than the historical average. 

“Gateway Park (32 miles downstream) had a 70 percent reduction in trout numbers and Lyons Park (42 miles downstream) had a 45 percent reduction in trout numbers. It was not until Lee Martinez Park (46 miles downstream) that 2021 trout numbers were within historic averages,” CPW said in a news release. 

Several species of fish were found dead along the way including trout, longnose dace, white suckers, and longnose suckers. 

CPW is advising fishermen to not fish between Stove Prairie and Black Hollow Creek. Anglers will have a better shot of catching trout upstream from the Poudre River State Fish Hatchery or downstream of Stove Prairie. 

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