This summer, the Town of Nucla had discussed “sensitive fish,” but that the fish are not affected by discharge of Nucla’s treatment plant into Calamity Draw. Tim Pierce, Mayor Pro Tem who also works as operator of Mustang Water Authority, told the Forum the ammonia levels at the discharge site are fine and watched by the state. He said levels would be mitigated, if necessary.
The Forum wanted to know more about the sensitive fish and contacted Tony Bonacquista, of Colorado Parks and Wildlife (CPW). Bonacquista said the West End is interesting, with cold water moving to warm.
“It’s a tough time of year for all fish with flows low and the water heating up,” he said.
He referred the Forum to Dan Cammack, along with Zack Hooley-Underwood, both of CPW, for more information.
The “three species”
Hooley-Underwood told the Forum the Bluehead Sucker and the Flannelmouth Sucker are common in the San Miguel River. Both are Tier 1 status in Colorado but have no federal status. Tier 1 is the state’s prioritization of those most at risk.
The Roundtail Chub, he said, is present in the San Miguel but less common than the sucker species. They’re more common downstream and into the Dolores. Also Tier 1, they have no federal status.
“These three fish we commonly refer to as the ‘three-species,'” he said. “They are endemic to the Colorado River Basin and generally co-occupy habitats. All have been displaced from over 50% of their historic range, and are the focus of a range-wide conservation agreement between state, federal and tribal agencies. In Colorado, our aquatic biologists, native aquatic species conservation biologists, and myself, an aquatic research scientist, all actively work to secure and expand the distribution and abundance of these three fishes.”
He added the San Miguel and Dolores rivers are both occupied by the three species and collectively have one of the best populations in the state.
Fish that are thriving
Also, Hooley-Underwood said the Speckled Dace is common in the San Miguel River and throughout western Colorado, and there’s no state or federal status for it. Similarly, the Colorado Sculpin is common in the San Miguel too, especially upstream in Naturita and in western Colorado. No status has been applied to the latter either.
Those most at risk of extinction
On the other hand, the Colorado Pikeminnow is extremely rare in the San Miguel and Dolores rivers.
“We do have (RFID) tag detection data that indicates a few have moved through the Dolores, and at least one has entered the San Miguel in recent years, but these fish really aren't found in the Dolores drainage anymore, besides a few that frequent the lower miles of the Dolores,” he said. “Historically, they were likely fairly common in the drainage, though highly migratory, in and out of the Naturita area. The lack of dependable large runoff flows and sufficient summer and fall flows are the primary driver for their absence in the drainage nowadays.”
The Colorado Pikeminnow is at a Tier 1 status in Colorado and is also listed as endangered with the feds.
At the same time, the Razorback Sucker is extremely rare in both the San Miguel and Dolores rivers. Hooley-Underwood said it’s a very similar situation to the Colorado Pikeminnow, as the fish is Tier 1 for the state and just got downgraded from endangered to threatened federally.
The Boneytail Chub was likely present in the Dolores drainage historically, but not now. The fish is at Tier 1 for the state and threatened federally.
“Aside from Speckled Dace and Colorado Sculpin, all of the native fish in the Dolores and San Miguel rivers near Naturita and Nucla are at-risk of further population decline,” he said. “The biggest threats are manipulations to the natural flow regime and non-native fishes.”
What CPW does to support the native fish
Hooley-Underwood said in the Dolores River especially, the overall lack of sufficient flow year-round makes it difficult for this highly migratory group of fish to find or move between rearing, spawning, feeding and wintering habitats. In several short stretches of the Dolores, invasive Smallmouth Bass have decimated native fish populations. Throughout the Dolores and San Miguel rivers, Channel Catfish, Green Sunfish and Black Bullhead predate upon young native fishes, making it hard for populations to maintain historic levels.
“Despite these problems, the three-species still do fairly well in this river,” he said. “CPW stocks Bluehead Suckers in the Dolores near Dove Creek to supplement the population there, conducts Smallmouth Bass removals to support better native fish survival, conducts population assessments to monitor trends over time and tracks fish using passive integrated transponder tags and antennas to better understand when these fishes are moving and where."
