by John Livingston, Colorado Parks and Wildlife , Southwest Region Public Information Officer
MOSCA, Colo.—A decades-long effort to establish new populations of imperiled Rio Grande chub and Rio Grande sucker fish in Colorado’s San Luis Valley led to a historic day on the Medano Ranch of Great Sand Dunes National Park and Preserve.
Colorado Parks and Wildlife (CPW) collaborated with the U.S. Fish and Wildlife Service (USFWS) and National Park Service (NPS) this fall to translocate a population of Rio Grande chub and sucker from Crestone Creek in the Baca National Wildlife Refuge to Big Spring Creek in the Medano Ranch.
More than 600 fish were collected from Crestone Creek and transported to Big Spring Creek, where aquatic biologists hope to create a new self-sustaining population of the native fishes. Currently, there are only seven known self-sustaining populations of Rio Grande sucker in the state.
“This is just a good collaboration between the National Park Service, U.S. Fish and Wildlife Service and CPW and shows good common-sense management to replicate this resource in newly acquired habitat,” said CPW Native Aquatic Species Biologist Daniel Cammack. “Using these fish from Crestone Creek and moving them to a habitat where they are likely to thrive and start another population is a really great effort.”
Rio Grande chub and suckers are currently petitioned to be listed as federally endangered. In Colorado, Rio Grande chubs are listed as a species of special concern and have lost as much as 80% of their historical range within the upper Rio Grande Basin. Rio Grande suckers are a state endangered species, whose occupancy has declined as much as 90%.
The NPS acquisition of Big Spring Creek and the Medano Ranch from The Nature Conservancy presented a unique opportunity to restore these fish to historic habitat in the low gradient creek. The creek is sustained by a perennial supply of spring water that averages 5 cubic feet per second, making it pristine habitat for the native fish species.
Through consistent monitoring of Big Spring Creek, the NPS determined conditions would be suitable for Rio Grande chub and sucker. As soon as it was deemed quality habitat, all three agencies worked together to quickly populate the stream.
“This is a great opportunity to replicate an imperiled population from 20 miles north of us on the Baca Refuge,” said Dewane Mosher, biologist for Great Sand Dunes National Park. “It’s important to secure those genetics from the wild fish here in the National Park.”
Crestone Creek exists on the Baca National Wildlife Refuge, adjacent to Great Sand Dunes National Park and is roughly 20 miles north of the Medano Ranch. Fish were first discovered in Crestone Creek in the early 2000s by Ron Garcia, manager of the Baca Refuge. CPW aquatic biologist John Alves identified the population of fish as Rio Grande chub and sucker, only the second known population of both species that existed at that time.
Since that important discovery, CPW has worked with USFWS to protect and expand the population on the refuge, which is considered one of the most important populations in the species’ range.
“This is an ideal opportunity and it was a historic day to restore some native fish into Big Spring Creek here at the Medano Ranch,” said Fred Bunch, Chief of Resources Management for the Great Sand Dunes National Park and Preserve. “We want to restore endangered species to their habitat. We are very optimistic about their chances of making it here. We want to help these species expand their habitat, and we want to be true to our word and do what we can to help these species.”
The translocation project also allowed CPW and the USFWS to salvage a portion of the population within Crestone Creek. The creek flowing through the Baca Refuge has fluctuating water flows and was running below 1 cfs in September. The Rio Grande chub and suckers occupied small pools where high densities could have led to natural mortality in the winter.
“Historically, Big Spring and Crestone would have been connected here in the Valley and fish may have migrated from one creek to another,” said USFWS Fish Biologist Cole Brittain. “However, with recent drying and lack of water from the abundance of agriculture and ranching related water use, we don’t have those same connections today.
“With the NPS acquiring this property, we can manually transport these fish, and that’s a unique opportunity. This project is 20 years in the making and one we wish we could replicate all over the place, but these properties don’t come by very often. It takes a lot of work from a bunch of agencies.”
Plans are in place to continue introducing more chub and suckers to Big Spring Creek in 2024 utilizing fish from CPW’s John W. Mumma Native Aquatic Species Restoration Facility and additional salvage of wild fish from Crestone Creek as opportunities are presented.
“Past experience with these reintroductions suggests that it can take anywhere from two to five years of stocking before a self-sustaining population is created,” Cammack said. “We will continue to monitor annually, hoping to detect young-of-year fish, providing evidence that natural reproduction is taking place.”
CPW, NPS and USFWS will remain committed to the protection and restoration of these fish to their native range, as projects such as Big Spring Creek align with their shared mission.
“They’re not the species people want to go out and catch on hook and line, but they are an important part of Colorado’s natural legacy,” Cammack said. “They evolved in this landscape, and if you want to consider the environment good as a whole, we want to keep all the pieces.
It’s important we not only pay attention to sport fish but also these native species that historically haven’t been managed very well.”