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CPW presents mixed fishery picture after river reconnection; tiger muskie used to tackle white sucker overpopulation
Summary
A Colorado Parks and Wildlife biologist told the Grand County commissioners that the newly reconnected Colorado River reach shows strong biomass and early rainbow trout recruitment but persistent brown trout recruitment problems after wildfire. CPW described a three‑year tiger muskie stocking trial in Shadow Mountain Reservoir to reduce a large white sucker population and noted monitoring and spill‑risk safeguards.
John, a Colorado Parks and Wildlife fisheries biologist, briefed the Grand County Board of County Commissioners on the status of local fisheries following the Colorado River connectivity project and other recent management actions.
CPW reported that a May 2025 electrofishing survey of a 6,600‑foot reach of the reconnected Colorado River produced an estimated biomass of roughly 123 pounds per surface acre and about 31 fish over 14 inches per acre—figures that exceed CPW's trout biological criteria. The biologist said those fish colonized the channel naturally and that CPW later stocked roughly 350,000 wild‑type rainbow trout fry to bolster recruitment.
The presentation emphasized uneven recovery: brown trout recruitment on many upstream reaches remains well below pre‑fire levels, a decline CPW attributes to post‑wildfire sediment and habitat disruption. "Since the fire we have not had good brown trout reproduction and survival," the biologist said, noting only partial recovery downstream of the Williams Fork confluence where tributary production contributes juveniles.
On reservoir management, CPW described a three‑year pilot at Shadow Mountain Reservoir that uses sterile tiger muskellunge (tiger muskie) to reduce an overwhelming white sucker population. CPW's netting surveys estimate 140,000–200,000 pounds of white sucker in Shadow Mountain; tiger muskie stocking in 2023'025 yielded detectable predation patterns and a 9% representation of tiger muskie in the 2025 gillnet catch. "They're doing exactly what we were hoping they'd do," the biologist said, while acknowledging tradeoffs: a reduced trout fishery in Shadow Mountain during the trial and some tiger muskie spilling into connected waters.
To manage spill risk, CPW said it is liberalizing harvest rules in non‑target waters (Granby, Grand Lake, portions of the Colorado River downstream of Shadow Mountain Dam) and retaining a conservative statewide regulatory framework within Shadow Mountain itself. CPW also reviewed monitoring plans, netting data and a new regulation effective April 1 that adjusts angling rules around tiger muskie presence.
Commissioners and CPW staff discussed implications for kokanee and lake trout in Lake Granby, habitat responses to drought, and expectations for multi‑year recovery. The biologist invited the public to a "State of the Fish" presentation at Granby Public Library on March 10 for further detail.
CPW provided technical survey results and described planned follow‑up monitoring; no formal county action was requested at the meeting.
Ending: The commission thanked the CPW presenter and noted the material would inform ongoing regional water and fisheries planning.
