Date: 4/08/07
Contact: C. Doug Nielsen
Phone: (702) 486-5127, ext. 3500

ROUNDING UP RAZORBACKS

Mention cowboys and roundups to people familiar with Nevada’s heritage and they generally think of wide-brimmed hats, boots, chaps, lowing cattle and long, dusty days in the saddle. While that mental picture is accurate, there is another kind of roundup that is tied to an important part of the Silver State’s history. But rather than boots and chaps the cowboys wear boat shoes and waders. It’s the annual Razorback Roundup at Lake Mohave.

The razorback sucker is an endangered fish species that is native to the Colorado River system. At one time these fish were found in Wyoming, Colorado, Utah, Nevada, Arizona, and New Mexico. That is no longer the case, so every March fisheries biologists from multiple organizations gather at Lake Mohave to roundup razorback suckers, gather age and population data, collect larvae and release hatchery-raised fish into protected backwaters. All this is done to ensure the razorback’s future and has been occurring every year since recovery efforts began in 1989.

“Lake Mohave has the largest remaining population of razorbacks. We’ve been working with the Bureau of Reclamation, the U.S. Fish & Wildlife Service, Arizona Game & Fish, Arizona State University and the National Park service to maintain this population because it has the highest genetic diversity of existing populations,” said Mike Burrell, who has spent the past 26 years working as the Nevada Department of Wildlife fisheries biologist on Lake Mohave.

Two factors that have had a significant impact on the razorback population are the construction of dams and the introduction of non-native fish species. Historically the Colorado River was silty and the razorback evolved in that environment where it was difficult for predators to see the fish. That is no longer the case because much of the silt settles out behind the dams.

The razorback’s “natural reaction to predators is just to sit still. In a silty environment that’s fine, but in a clear water environment like most of the river is now, predators can see them easily and the razorbacks don’t have the avoidance ability they once had,” Burrell said. “I have even seen coyotes take them out of the water.”

Predatory fish species such as largemouth bass, bluegill, tilapia, green sunfish and crayfish also prey on razorbacks. Although adult razorbacks can reach lengths of over 30 inches, virtually all of the young fish are lost because of the changes to their habitat and predation by nonnative fishes.

A significant component of the Razorback Roundup is the gathering of larvae from the razorback’s spawning areas. These larval fish are raised in the predator-free environment of a fish hatchery until they are large enough to be reintroduced into protected backwaters of Lake Mohave and too big for most predatory fish to eat.

In addition to gathering larval razorbacks, the biologists also collect a sample of adult fish. These fish are counted, weighed, measured and scanned electronically to determine whether they are carrying a pit tag. Pit tags are a very small electronic device that is inserted just below the skin on the underside of the fish. Each pit tag emits an electronic identification number that is used to keep tabs on the individual fish that carries it. “These tags allow us to estimate the population and monitor the growth rates of individual fish,” said Burrell.

Eight to 10 years ago, the population of razorback suckers was estimated to be upwards of 50,000 fish. That number has since dwindled to about 5,000 fish in Lake Mohave, and that number includes older adult fish and the young fish planted through conservation efforts. However, the razorbacks do have one advantage; adults can live to be around 50 years old. That natural longevity has given biologists time to develop a strategy to prevent their extinction.

“We have been able to maintain this small population with what we have been doing. Unfortunately, we haven’t had the survival rates we had hoped for in the beginning. Without a long-term program, and the long life span of these fish, the outlook would be that the razorback will slowly disappear,” Burrell said.

The Nevada Department of Wildlife (NDOW) protects, restores and manages fish and wildlife, and promotes fishing, hunting, and boating safety. NDOW’s wildlife and habitat conservation efforts are primarily funded by sportsmen’s license and conservation fees and a federal surcharge on hunting and fishing gear. Support wildlife and habitat conservation in Nevada by purchasing a hunting, fishing, or combination license. For more information, visit www.ndow.org.