John Hawkins speaks of the Yampa River with reverence.
"The Yampa is unique," he said Friday near its bank west of Craig. "It is one of the last free-flowing rivers. It has a natural ecosystem, so it's special."
But the health of the river's native fish population is in danger. The Colorado pike minnow, humpback chub, razorback sucker and bonytail are endangered because non-native fish such as pike and smallmouth bass are flourishing.
The pike feed on native fish, and the bass feed on everything, hindering native fishes' ability to spawn and eat.
Hawkins and a research team based out of Colorado State University's Larval Fish Laboratory are studying a 24-mile stretch of the Yampa between Craig and Maybell to gauge the damage non-native fish have caused.
"Why are we doing it?" Hawkins said, repeating the question out loud. "It is for the science. If we want to rescue the native fish, the bass and pike need to be controlled. It if kept going the way it was going, the native fish in this reach of river would likely disappear,"
CSU began its research project in 2000. For six years, biologists from the Colorado Division of Wildlife, the U.S. Fish and Wildlife Service and CSU have been tracking the fishes' length, weight and location when they are caught.
The Fort Collins-based crew arrived last Tuesday and leaves Wednesday, spending nearly 12 hours a day on the water conducting research.
On Friday, the crew of seven put three boats in the Yampa shortly after 9 a.m. Less than 20 minutes later, they began their research.
Four silver balls charged with 110 volts of electricity hung from the front of two boats, shocking fish to the surface. The electricity attracted the fish and briefly stunned them, allowing researchers to net them for study.
The two boats unloaded their catches into a chase boat, where the fish were measured, weighed and examined. About half already had been tagged. The rest received a small tag and were released. Most of the fish caught Friday were smallmouth bass, demonstrating their prevalence.
It was encouraging that few pike were caught.
"It's a sign that we are having an effect," Hawkins said of the decreasing pike population.
It is thought the non-native fish were introduced to the Yampa via the Elkhead Reservoir near Craig. The pike likely entered the Yampa in the late 1970s, Hawkins said. Bass were identified in the mid-1990s.
Bluegill, black crappie and green sunfish are other non-native fish living in the Yampa. On Friday, a brown trout and rainbow trout, non-native to this stretch of the Yampa, were netted.
At the end of this study period, the crew will begin removing bass from the Yampa and relocating them to Loudy-Simpson Park in Craig. All fish, including the bass and pike, have value.
"But it's recreational," Hawkins said, about the usefulness of bass and pike in Colorado. "And you can get that other places than the Yampa."