Colorado Parks & Wildlife biologists and researches haves reported a "troubling" decline in greenback cutthroat trout populations.

For decades, many thought that Colorado's official state fish was extinct. After the fish resurfaced, the greenback cutthroat trout was adopted as Colorado's official state fish on March 15, 1994.

CPW has spent several years working to build back the population that is considered a threatened species by the U.S. Fish and Wildlife Service.

 “Since 2008, we have surveyed Bear Creek every three years to assess the size and health of the greenback population,” said senior CPW biologist Josh Nehring in a press release. “We only surveyed every three years to minimize stress on the fish.

“This September, we surveyed four reaches of the creek and the results were troubling. They suggested up to an 80 percent decline in the adult population. However, a fairly robust class of immature fish suggests that adults were still common and prolific until recently.”

CPW has launched a full investigation on what exactly is causing the decline.

“We have looked into several factors that may have contributed to this decline including water quality, temperature, flow, sediment accumulation, disease and the possibility of some unnatural human-caused event,” Nehring said. “At this point, we cannot say there is one single, definitive cause.”

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Colorado's Wild Big Game Populations