Innovative New Survey Method Reduces Stress on Threatened Fish

Since arriving in Colorado Springs in 2016, aquatic biologist Cory Noble has shouldered a huge responsibility for CPW: protecting tiny Bear Creek and preserving this critical wild population of greenback cutthroat trout.

Now, after a year of experimenting with technology, Cory says he has developed an innovative new way to reduce the stress on the threatened fish while giving biologists a better view than ever of their world. 

In fact, his new surveying method provides a 360-degree, high-definition, wide-angle view of the diminutive greenbacks swimming in the slender creek that twists and turns through heavy brush and boulders in a steep canyon on the southwest edge of Colorado Springs.

The greenback cutthroat, Colorado’s state fish, has been the focus of more than a decade of intensive efforts by CPW as the agency works to rescue it from near extinction and restore it to its ancestral waters in the South Platte River drainage to the north.

As the primary aquatic biologist for the Pikes Peak region, Cory has had responsibility for overseeing the creek and its precious residents. Spring, summer and fall, he pulls on decontaminated waders, straps on a heavy electrofishing backpacks, grabs buckets and long-poled nets and slogs up the creek, pushing through thickets of brush, negotiating slippery rocks and even climbing small waterfalls and through concrete culverts to study the greenbacks.

He wants to make sure the greenbacks, which live in the upper 5-mile stretch of Bear Creek, are protected from other, more aggressive fish that might swim upstream, from sediment pouring into the creek from canyon walls, from pollution in the water, habitat destruction and more.

Each May, Cory faces perhaps his most critical assignment of the year when spring runoff raises flows in Bear Creek, temperatures rise and the greenbacks start to spawn. Timing is critical as Noble leads a team of biologists, wildlife officers and staff, again carrying heavy electrofishing backpacks, as they painstakingly hike up Bear Creek to catch greenbacks and collect milt and roe – sperm and eggs – and spawn them on the banks of the creek.

Over the years, Cory has worried the fish might be getting stressed from frequent surveying with electroshocking equipment in the tiny creek, a process that includes scooping them into nets and dropping them into buckets. Stress on fish causes them to be less likely to reproduce.

Spurred by a 2020 scare when greenback numbers dropped unexpectedly, Cory went to work on a new, noninvasive way to survey Bear Creek that would put far less stress on the greenbacks. 

Recently, Cory announced to his CPW colleagues he had successfully developed a system using a 360-degree underwater camera that, when paired with virtual reality software on a computer or cellphone, allows him to actually look underwater and see exactly what fish are living in the creek. 

Already it’s producing vivid video of greenbacks darting about pools, hovering beneath riffles and even investigating the camera. And he’s learned that pools in the creek show a relatively high occupancy of multiple age classes of greenbacks.

“Cory’s creativity and innovation here has been outstanding,” said Paul Foutz, CPW’s senior aquatic biologist in the Southeast Region. “What Cory has developed is a novel system that protects the rare greenbacks while giving us an even better look under the surface of Bear Creek. It has potential for wider applications in creeks and rivers across Colorado where protecting a rare or sensitive fish species is of critical importance.”

Cory said he was inspired because he recognizes that while routine electrofishing typically does not harm fish, the repeated electrofishing and handling required to protect greenbacks from invasive species in Bear Creek and to monitor their health has the potential for mortalities and injuries to fish. Just wading into the creek carries the risk of introducing disease or aquatic nuisance species even though CPW follows strict decontamination protocols.

So he bought a wide-angle digital video camera designed for underwater use that provides views in all directions. Then he experimented with ways to anchor the camera underwater to allow standardized video sampling.

After mounting the camera on a large clay brick, Cory quickly devised a steel plate base to hold the camera. A steel rod attached to the base loops over the camera allowing Noble to drop the camera straight to the creek bottom and is sturdy enough to withstand currents.

“This is similar to snorkel surveys in that we get a clear picture of the underwater environment,” Cory said. “There is no body contact with the water, handling of the fish and no electricity involved.

“And the camera provides us a complete sphere of visibility so there is greater fish detection. This allows consistent observation of the fish and I only have to watch a single video file to see fish in all directions.”

Cory is using the data he collects to create a habitat occupancy estimate of the greenbacks in the creek. And now he is able to calculate the proportion of habitat that is occupied by greenbacks based on these visual observations, not just on the number of fish attracted by the electro-fishing equipment and scooped up in nets.

Cory and his team spent hours dropping the camera into randomly selected points along the creek and gathering video in 10-minute segments. He then had to study and evaluate the hours of video. Each video was watched and scored by two independent viewers. They kept precise data on observation locations, elapsed time, number of adult fish recorded, subadult fish and more.

“It’s a time-consuming process but I’m very encouraged that we were able to gather important information and minimize the amount of disturbances to the fish,” Cory said. “This method appears valuable and allows for an additional and noninvasive sampling technique.”

He’s so encouraged he hopes to purchase additional cameras to allow two or more teams to collect data more efficiently and hopefully ensure a thriving population of greenbacks in Bear Creek well into the future.

Written by Bill Vogrin. Bill is a public information officer for the Colorado Parks and Wildlife southeast region.