Double the Dace

This fish is in hot water, and likes it!

Michael Schwemm inspects a glass viewing area.

Moapa dace are found only in the Muddy River Springs area, composed of the Moapa Valley National Wildlife Refuge streams, adjacent private estates and the Warm Springs Natural Area. Credit: USFWS


Pacific Southwest Region External Affairs
November 6, 2019

For 50 years, the U.S. Fish and Wildlife Service has worked to save the endangered Moapa dace, a tiny olive-yellow colored fish found solely in Southern Nevada’s Moapa Valley. This listed fish species is special since it has no relatives around today and therefore represents a unique component of biodiversity.

a close up of a Moapa Dace.

Native to Southern Nevada, the Moapa dace reproduces year-round and reaches maturity in one year. Photo courtesy of David Syzdek

Moapa dace are found only in the Muddy River Springs area, composed of the Moapa Valley National Wildlife Refuge streams, adjacent private estates and the Warm Springs Natural Area - approximately 1,200 acres owned and operated by the Southern Nevada Water Authority. This species is restricted to the warm headwaters where springs emerge and only occur in water temperatures between 86 and 90 degrees Fahrenheit.

In the mid-1990s, the fish was on the brink of extinction with an estimated population size of about 500 due to early Moapa Valley settlers diverting channels and modifying stream habitat, as well as the introduction of non-native fishes. The 116-acre national wildlife refuge was the first of its kind dedicated to the habitat and recovery of this listed species.

In recent years, the Moapa dace population has increased and now averages between 1,000 – 1,500. Although much has improved due to ongoing habitat restoration projects, this species remains endangered because numbers are still too low to be considered safe from extinction.

Michael Schwemm deploys a fish trap in the Muddy River Springs area.

Michael Schwemm, U.S. Fish and Wildlife Service biologist, deploys a fish trap in the Muddy River Springs area. Credit: USFWS

The Service individually counts the number of Moapa dace biannually with the assistance of partner agencies, the Southern Nevada Water Authority and the Nevada Department of Wildlife. Researchers slip on wet suits and snorkels and swim the entire network of vibrant streams to count individual Moapa dace. Counting the population enables researchers to observe the species survival and reproduction rates, or if they’re declining and how best to focus recovery efforts.

U.S. Fish and Wildlife Service biologist Michael Schwemm evaluates the status of Moapa dace and seeks opportunities for species conservation by developing recovery plans, guiding research and coordinating recovery work with partner agencies.

“As a biologist, we get to spend time outdoors and look at species in their natural habitat – see fish, count fish and document their life history,” explained Schwemm. The recovery goals of the U.S. Fish and Wildlife Service strive to increase population size to approximately 6,000 adult fish occupying most of its historical habitat.

Michael Schwemm looks over a glass rail to inspect a water stream.

Michael Schwemm performs an inspection of the water streams where the Moapa dace live in the Muddy River Springs at Moapa Valley, Nevada. Credit: USFWS

One positive factor is that Moapa dace reproduce year-round. The fish lay eggs in calm warm spring waters and then travel downstream to larger habitat to feed and mature. Having a clear path for the Moapa dace to travel back and forth throughout their life cycle is essential for their survival, which is why habitat maintenance is critical for this species. Biologists remove fallen branches, overgrown brush or other obstacles to reduce obstruction of the dace’s migratory path.

shot of water with green plants visible on the bank.

By controlling vegetation growth and manipulating the habitat, partner agencies can keep the water moving fast and keep it warm which is what the Moapa dace needs to survive. Credit: USFWS

“By controlling vegetation growth and manipulating the habitat, we can keep the water moving fast and maintain its warm temperatures, which Moapa dace need to survive,” said David Syzdek, an environmental biologist with the Southern Nevada Water Authority. “Those habitat improvements really increased the dace numbers to well over 1,000.”

Habitat conditions for the Moapa dace are improving, and fish abundance is responding positively due to partnerships with the National Fish Passage Program, Desert Fish Habitat Partnership, state agencies, local volunteer groups and more.

“Because the habitat and streams are small, we can make modifications that improve the probability of success for this species,” said Schwemm.

The public is invited to experience the Moapa dace first-hand by visiting the Moapa Valley National Wildlife Refuge in Moapa, Nevada and especially visit the glass viewing area where the fish regularly swim.

two men stand on a small bridge with trees around them.

Michael Schwemm, U.S. Fish and Wildlife Service biologist, right, and David Syzdek, an environmental biologist with the Southern Nevada Water Authority encourage the public to visit the Moapa Valley National Wildlife Refuge in Moapa, Nevada and witness the reslience of the Moapa dace in its desert habitat. Credit: USFWS

Directions to the Moapa Valley National Wildlife Refuge

Due to its small size, fragile habitats, and on-going restoration work, the wildlife refuge is only open Friday, Saturday and Sunday, sunrise to sunset, from Labor Day through Memorial Day. The wildlife refuge is closed from Memorial Day until Labor Day.

From Las Vegas, drive north on Interstate 15 to the Moapa/Glendale exit (#90). Go straight (northwest) on Highway 168 for 7.4 miles to Warm Springs Road. Turn left (southwest) on Warm Springs Road and drive for 1.4 more miles. The refuge is on your left, when you see the chain link fence on both sides of the road.

From St. George, Utah or Mesquite, Nevada, drive south on Interstate 15 to the Glendale/Moapa exit (#91). Turn left (southwest) onto E. Glendale Blvd. Merge/turn right (northwest) onto Highway 168 for 7.4 miles to Warm Springs Road. Turn left (southwest) on Warm Springs Road and drive for 1.4 more miles. The refuge is on your left.