Weather allowing for fish studies

What are being called "perfect flow conditions" this year have enabled biologists to conduct four important research studies in the Green River in northeast Utah to gain information needed to help recover the razorback sucker.

The Green River system is considered vital to recovery of the razorback sucker and three other endangered fish species — the humpback chub, bonytail and Colorado pikeminnow.

Designed in cooperation with the Upper Colorado River Endangered Fish Recovery Program, the studies had been postponed for several years due to the drought.

Three of the studies focused on learning how drifting razorback sucker larvae are transported by water currents out of the fast-flowing river into the calmer waters of floodplain wetlands that serve as nursery habitat. The fourth study focused on measuring the amount of sediment deposited onto a razorback spawning site.

Successful completion of these studies depended on high spring flows that provide the habitat conditions that razorback suckers need to spawn and connect the river to floodplain nursery areas.

"This spring, the U.S. Bureau of Reclamation helped us keep a close eye on weather and river flow forecasts to determine if this would be the year we could conduct these studies," said Bob Murth, program director.

"When we realized that snowpack and warm spring temperatures would likely result in the high flows we needed, our partner agencies quickly rallied to launch the studies. We knew we would have a narrow window of opportunity to get out on the river and conduct our work."

The Bureau of Reclamation assisted the research by releasing some additional water from Flaming Gorge Dam for two days before and after the peak flow. This helped support the necessary flow conditions. For several days in May, more than 20 researchers and volunteers worked around the clock to simultaneously conduct the various studies.

The Utah Division of Wildlife Resources and Colorado State University took the lead to evaluate larval transport and habitat use. At each targeted flow, they released 3 million biodegradable, color-coded beads that simulated drifting larvae and between 100,000 and 400,000 marked razorback sucker larvae at razorback sucker spawning areas near Jensen, Utah.

They later captured the larvae and beads in drift nets as they entered selected floodplain habitats, some as far as 54 miles downstream from the spawning areas.