Wildlife Wednesday: Rio Grande Silvery Minnow Conservation

By Ben Neary

NMWF Conservation Director

The Rio Grande silvery minnow has been on life support for decades. A team at the Albuquerque BioPark is helping to keep the minnow alive even as the federal government recently cut funding for conservation work on the species.

Workers at the BioPark’s Aquatic Conservation Facility – tucked in behind the Botanic Garden in the heart of Albuquerque – raise and release thousands of silvery minnows into the Middle Rio Grande each year. The federal government and the state operate other minnow hatcheries.

Kathy Lang, aquatic conservation and operations manager at the BioPark and Patrick Horley, curator of the BioPark’s Aquatic Conservation Facility, will discuss their work on conserving silvery minnows. They will give a joint presentation at the New Mexico Wildlife Federation’s ‘Wildlife Wednesday” event on July 9. The free event will start at 5:30 p.m. at Marble Brewery’s Northeast Heights Taproom at 9904 Montgomery Blvd., NE, in Albuquerque.

The Rio Grande silvery minnow can grow to about 4 inches long. Their bodies are greenish-yellow on their backs and white or cream-colored on their bellies. They generally prefer slower water.

The silvery minnow was once one of the most common fish in the Rio Grande. Its population ranged as far south as Texas and as far north as the Rio Chama. Some lived in the Pecos River drainage as well.

These days, the silvery minnow exists in less than 10 percent of its historic range. It’s found only in the Middle RIo Grande, from Cochiti Pueblo downstream to the upper reaches of Elephant Butte Reservoir. 

The minnow population has fallen as increasing human demands for water from the river have combined with the effects of climate change. Stretches of the Middle RIo Grande commonly run dry in the summer months.

The U.S. Fish and Wildlife Service listed the minnow as an endangered species in 1994 and the state placed it on its endangered list two years later. The BioPark facility opened in 2000 and has been operated continuously since then by the City of Albuquerque.

Each year, workers at the BioPark rear and release about 50,000 of the minnows into the Rio Grande. The USFWS raises and releases about 200,000 of the minnows at its hatchery in Dexter. The New Mexico Department of Game and Fish raises and releases minnows from a hatchery in Los Lunas, as well.

Lang said fish from each hatchery are marked with a special color of paint on their backs so researchers can track how far they’ve moved in the river if they’re recovered later.

Lang was promoted to aquatic conservation and operations manager at the BioPark in January 2021 following seven years of overseeing the Aquatic Conservation Facility and Tingley Beach. Before joining the BioPark, Horley worked in commercial aquaculture and served in the Peace Corps.

Workers at the Aquatic Conservation Facility raise minnows from eggs collected from the Rio Grande. They also maintain a population of minnows to ensure they can continue the breeding program if egg-collection efforts don’t yield enough in any year.

Lang said workers collect minnow eggs from spawning areas in the Rio Grande wherever they can find them. “We’ll try all three reaches – the Albuquerque Reach, Isleta Reach and San Acacia,” she said.

Conserving the minnow is important because of its endangered species status, Lang said. But she said work to protect the minnow has other benefits as well.

“Because of the endangered species status, that also protects its habitat,” Lang said. “So that protects the river for birds and bugs and plants and everything. If the silvery minnow goes away, habitat protection goes away. I think the whole river would be dry, basically, seasonally of course. It’s part of our food chain, part of an ecological system, so you don’t ever know really what’s going to happen if you take out a piece.”

In the decades since the minnow was federally listed as endangered, state, federal and local agencies have coordinated their conservation efforts.

The BioPark is one of 17 member organizations of the Middle Rio Grande Endangered Species Collaborative Program. The effort includes local, state and federal agencies as well as Indian pueblos and other organizations. They work to conserve the minnow and other endangered species along the Middle Rio Grande.

Early this year, the Trump Administration canceled a federal contract of almost $1 million a year that pays for a third-party manager to oversee and coordinate efforts among the various organizations involved in the collaborative program.

Lang said the BioPark operation has received more than half its funding directly through the U.S. Bureau of Reclamation. She said that funding will stop in October as a result of the contract cancellation. She said she’s writing proposals seeking grant funding to make up the shortfall.

The Albuquerque Bernalillo County Water Authority contributes some funding to the BioPark for the minnow work. The authority, which used to be a city agency, takes water from the river.

The BioPark program costs about $200,000 a year, including four employees and temporary workers during the spawning season, Lang said.

The BioPark facility keeps fish in rearing pens, segregated by age and the different locations of the Rio Grande they came from. It also has a pond where pumps can generate current in the water to simulate river conditions.

In addition to raising the minnows, the BioPark facility also raises rare Socorro Isopods as well as a number of rare fish species from Mexico.

In order to get the minnow off the federal endangered species list, Lang said it would have to have three self-sustaining populations. The population in the Middle Rio Grande is not self-sustaining and efforts to establish another population in the Big Bend area of Texas proved unsuccessful, she said. 

“Right now, this is the only population, and we’re trying to keep it self-sustaining and it just depends on the river,” Lang said. “If it’s a dry year, you may lose most of the population. If it’s a wet year, we may get a whole lot of fish produced, which is awesome because they reproduce in large numbers. So they can recover within a few years of a dry year, but if you get like three dry years in a row, they’d be done without intervention.”

Lang is reserved when speaking about her view of the future of the minnow.

“I see that we can maintain this population the way we’re doing it,” Lang said. “But if we can’t get a second population established somewhere, then we’re just treading water. 

“The river’s not what it used to be,” Lang said. “So I don’t think recovery’s going to happen spontaneously. We can’t put enough fish in the river to overcome the physical challenges. So we just have to keep doing it as long as the physical challenges exist. The dams aren’t going anywhere, and the weather’s probably not going to change favorably, so we can keep doing what we’re doing but we really need another favorable location, for the benefit of the species.”