A Nursery for Endangered Fish – 2023 Update

Engineers have widened the river channel, allowing the water and larval razorback suckers to enter the preserve, floating through a control gate and into the central pond. After several months of safely growing in the preserve’s pond, the more mature fish are released back into the river’s mainstem in early fall.

The goal for this project? Restore what has been disrupted on the river through years of human impacts, and re-establish a wild, self-sustaining population of an endangered species.

A River Forever Changed

More than 100 years ago, razorback suckers thrived throughout the Colorado River Basin, at home in the swift waters of the free-flowing rivers in seven states and Mexico. They often migrated hundreds of miles in one year and grew up to 3 feet in length.  But then the Colorado River entered a new era: one of dam building, increasing water withdrawals and sport fish stocking. Like other native fish, the razorback suckers began to die off, veering toward extinction as the Colorado River’s flows and habitats were altered. 

Climate change—and its deepening impacts on the entire Colorado River Basin—hasn’t helped. Intensifying high temperatures and on-going low precipitation have caused river levels to drop steadily, with predictions even more dire for the future. “We used to say it’s a drought,” Taylor Hawes, TNC’s Colorado River Program Director, told the Durango Herald last summer.  “After 19 years, we can say this is a pattern and trend that is punctuated by super dry years like 2002 and 2018.”

The sad reality is that for many native fish like the razorback sucker, the Colorado and its tributaries are drastically less livable.

It's a Hard-Knock Youth

Since 1991, when the razorback sucker was placed on the Endangered Species list, conservation partners and state and federal agencies have been working throughout the Colorado River Basin to bolster populations. One key challenge is getting the fish in the wild to survive past their larval and juvenile phases. For reproduction and the first year of life, razorback suckers need slow-moving, back-eddy waters—a type of habitat that has been dramatically reduced along the Colorado as dams change flow dynamics and invasive plants crop up along river banks.  To make matters worse, over the past 100 years, more than 70 non-native fish species have been introduced into the Colorado River Basin, many as sport fish.  These invasive species wreak havoc on the river’s native ecosystem.  Razorback sucker eggs and juveniles are easy prey for toothed non-native predators.

Discovery at the Matheson Preserve

A few years ago, at TNC’s Scott M. Matheson Wetlands Preserve along the Colorado River near Moab, biologists made an exciting find while sampling for native fish. They uncovered a surprising number of wild-born razorback sucker larvae along the shoreline of the preserve. In fact, the scientists concluded the Matheson Preserve provides the only suitable nursery habitat for this species along 65 miles of the river. Encouraged by these findings, and the prospect that there could be a way to help these fish reach adulthood in the wild, TNC joined forces with the Utah Division of Wildlife Resources, Jones and DeMille Engineering, and PE Engineering to transform the preserve’s central pond into a protective nursery habitat for the fish.

Creative Engineering

Inspired by a similar effort on the middle Green River near Jensen, Utah, the team of scientists and engineers modified a portion of the preserve’s wetlands by widening an existing channel from the Colorado River to the preserve’s central pond. This allows more water into the preserve during spring runoff—the time when the larvae need a safe place to grow. 

Engineers have also designed a control structure to channel both the water and the razorback larvae into the preserve. This unique structure is key for the nursery to succed. The concrete channel has a control gate and screen system that only allow larval fish to pass while keeping larger non-native predatory fish from entering. The structure also includes a fish capture area where the young fish can be measured and tagged before being released back to the Colorado River.

This fish nursery—the first on the Colorado River—could become a proven solution to help other threatened or endangered fish recover in western rivers.

TNC extends special thanks to the Department of Natural Resources Endangered Species Mitigation Fund Recovery Program, the Utah Watershed Restoration Initiative, the Utah Department of Transportation Mitigation Fund, and the Utah Division of Wildlife Habitat Council for their lead financial support on this project.

And stay tuned for updates as this endangered species rescue plan unfolds.