GRANBY, Colo. — Colorado Parks and Wildlife (CPW) saw an increase in the native fish population numbers more quickly than anticipated in the recently completed Colorado River Connectivity Channel (CRCC) project at Windy Gap Reservoir, located near Granby, Colo.
In early May, CPW Aquatic biologists completed the first-ever raft electrofishing survey to estimate the trout population in the CRCC. Biologists estimated that approximately 848 brown trout and 221 rainbow trout over 6" in length live within a one-mile reach of the newly constructed river channel.
"It was very exciting to see a healthy number of adult trout occupying all of this new habitat," said Jon Ewert, CPW Hot Sulphur Springs Area Aquatic Biologist. "Especially considering that we have not stocked a single fish into the channel.”
As a result of the improved habitat, trout from connected river sections both upstream and downstream have been able to re-establish in the newly reconnected section of the Colorado River. CPW biologists also observed extensive brown trout spawning activity in the channel last fall and moderate rainbow trout spawning activity this spring.
“Seeing such positive results with water flowing through this new river section for just over a year, we anticipate that this fish population will continue to grow,” said Ewert.
Click to watch: Videos from this year's Colorado River Connectivity Channel fish survey
This is the second time CPW has documented positive signs of native fish repopulating the CRCC earlier than anticipated. In the fall of 2024, CPW's aquatic research team found evidence of native sculpin returning to the upper Colorado River and the CRCC after several decades of absence in nearly 30 miles of their former habitat. Sculpin found in the CRCC and downstream in the Colorado River included fish that were spawned and hatched in 2024.
During the survey, researchers documented one adult and 11 juvenile sculpin within the CRCC and a single juvenile sculpin in the Colorado River below the channel. Based on these sampling results, aquatic biologists and researchers from CPW believe that young sculpin are now able to take advantage of the new habitat and are dispersing downstream from healthy populations located upstream of the CRCC.
“The rapid colonization of the CRCC by this unique native fish species and its return to the Colorado River below Windy Gap is an important conservation milestone and a good indication that the channel is starting to improve the ecological health of the river," said Dan Kowalski, CPW Aquatic Research Scientist.
While the beneficial effects of the CRCC may take years to be fully realized, the results from the fish surveys conducted in May 2025 and fall 2024 represent significant milestones in the efforts to enhance habitat conditions in the upper Colorado River. These findings suggest that the health of the river may be improving more quickly than expected.
Completed in the fall of 2023, the Colorado River Connectivity Project is one of the largest aquatic habitat improvement initiatives ever undertaken in Colorado. This project reconnects aquatic habitats that were fragmented by the construction of the Windy Gap Reservoir in 1985. Currently, the new river section is closed to public fishing access. It is expected to open after the area has had sufficient time to fully revegetate, which will take a couple more growing seasons. To learn more about the Colorado River Connectivity Channel Project, visit the project's page on Northern Water’s website.
