Diverse Group Unites to Save Endangered Minnow

It might have been just another battle lost in the war against invasive species: The blue tilapia, a fish native to the Nile River, was muscling its way into a delicate desert ecosystem in Nevada.

But this invader made the mistake of picking on the rare Moapa dace, a minnow protected by the Endangered Species Act.

The dace’s predicament has prompted an unusual degree of cooperation in this independent-minded area. Private landowners, environmentalists and state and federal officials have joined forces to keep the voracious tilapia from decimating the dace, a species found only in the shallow, lukewarm headwaters of the Muddy River.

Usually no bigger than a man’s index finger, the Moapa dace is known to biologists as a thermal endemic, singularly adapted to the 90-degree streams flowing from the Warm Springs area 60 miles north of Las Vegas. Cold water downstream has kept the species from spreading outside its small original habitat.

“It’s a very elegant fish,” said Gary Scoppettone, a biologist with the U.S. Geological Survey in Reno.

The tilapia, by comparison, is a brute. It resembles a bluegill or crappie and can grow to 16 inches long. Illegally introduced here in 1991, probably by sport fishermen, the species has thrived near Moapa, spawning year-round in the warm water and eating vegetation that supports aquatic insects.

“Once they’ve completely eaten out the vegetation, they start in on the dace,” said Cynthia Martinez, Muddy River project coordinator with the U.S. Fish and Wildlife Service. “It’s like they go to the salad bar and when the salad is gone, they go to the meat.”

The dace’s numbers have declined to fewer than 1,000 from a peak of about 4,000 in 1994.

One fortunate break: The tilapia haven’t spread to the streams of the Moapa Valley National Wildlife Refuge, a vital holdout for the dace.

“Sheer luck, sheer luck, sheer luck,” said Bruce Lund, a Nature Conservancy official. “There was one small natural waterfall that prevented them from getting into the stream system.”

Helping that core population of dace reclaim waters invaded by tilapia is the goal of the Muddy River Recovery Implantation Team.

The group unites a diverse cast of characters, with representatives from the Nevada Division of Wildlife, the private Nature Conservancy, the U.S. Bureau of Reclamation, the Southern Nevada Water Authority and a handful of local citizens calling themselves the Muddy River Regional Environmental Alleviation Committee.

Stated simply, the team’s plan is to evict the tilapia and help the dace move back in.

Last spring, about 300 dace were captured and held in tanks while biologists poured a natural toxin, rotenone, into a narrow creek called Apcar Stream. Once the tilapia all died and the poison was neutralized, small dams were built to prevent tilapia from moving in from elsewhere, and the captured dace were returned to Apcar Stream.

It was a small step. Most of the dace’s habitat still is occupied by tilapia. But biologists and bureaucrats count a bigger victory in having won the cooperation of Moapa residents, Martinez said.

At first, landowners were reluctant to let government officials cross their property. Mary Premo, age 90, said she’d never seen anything bigger than a minnow in the stream running near her house and didn’t want the government pouring poison into it.

But the citizens committee has been key in swaying local opinion, reassuring neighbors that the feds aren’t trying to take their land or prevent them from using the river.

Premo heard from Ann Scheriber, Moapa Town Advisory Board chairwoman and director of the citizens committee.

“Bless her heart,” Scheriber said. “The only thing I did after Mary Premo said they couldn’t come on her property was, I talked to [her], and then she said it’s OK.”

Lund said it also helped when Premo hooked a tilapia in the stream. She fed it to her cats.

“I tell my staff the most important thing we can do is to meet people, interact with people,” Lund said. He and his wife sing in the valley chorus. He also serves as an advisor to the citizens committee and sits on the town board.

“It’s one thing to say, ‘It’s the law to protect these fish,’ ” Lund said. “It’s another to say, ‘Hey, we’ve got these fish here that are pretty special and we’d like to work with you to protect them.’ ”