Does the fate of the silvery minnow foretell the Rio Grande's future?

Biologists go to great lengths to keep the fish alive, but it’s nearly extinct in the wild.

 

On a cloudy May morning after a pre-dawn rainstorm, biologist Kimberly Ward winds through the Albuquerque BioPark’s Aquatic Conservation Facility, one of three hatcheries for endangered Rio Grande silvery minnows. Inside, pet-shop-sized fish tanks hold about 8,000 nearly invisible eggs.

Outside are the 20,000-gallon pools that host the fish after they hatch, as well as a massive concrete “raceway” designed to mimic a river and encourage them to spawn without hormone injections.

There’s always a challenge: Minnows spawn in the raceway, but their eggs get sucked into its intakes. Biologists also struggle with wonky pH levels in the tanks, and bacterial infections can spread. And conditions aren’t much better in the minnow’s natural habitat, the Rio Grande. Sometimes, Ward finds it hard to be optimistic.

“But I feel pretty lucky to be part of a program that’s fighting for species diversity,” she says, adding that saving the minnow is about more than one species; it’s about the entire river. “If we lose the fish, something worse is probably coming down the pike. It’s an indicator.”

If that’s true, the prognosis seems grim. For about a decade, scientists, environmentalists and water managers have gone to great lengths to keep silvery minnows alive, in accordance with the Endangered Species Act. It’s not easy. Each spring, when the Rio Grande rises and the fish spawn, biologists collect eggs as they float downstream. When the river channel dries south of Albuquerque during irrigation season — as it has almost every year since 1996 — the scientists grab fish from shrinking pools and truck them to still-wet downstream stretches. After Halloween, when irrigation canals stop diverting water and the dry stretches regain some flow, the tanker trucks arrive, bearing minnows raised in hatcheries from eggs collected earlier in the year. 

And yet the minnow’s numbers continue to decline. Agencies have devised new plans, built partnerships, and spent more than $150 million to boost the population. But the effort nibbles at the edges of a systemic problem: Fish need water, and what with unrelenting drought, rising demand and a changing climate, there’s just not enough of it in the Rio Grande.


The fish — historically one of the river’s most abundant — hasn’t totally disappeared, but the wild population is functionally extinct. Today, it’s almost impossible to find one without at least one hatchery-reared parent. “The entire genetic trajectory of the fish is determined by a hatchery now,” says Thomas Turner, who started studying its genetics in 1999 at his University of New Mexico lab. “You get this false sense of security that technology can get you out of these environmental problems. The big question is: If we can raise them in the hatchery, why do we have to worry about the river?”

 

A Rio Grande silvery minnow is measured at the BioPark Aquatic Conservation Facility.
Albuquerque BioPark

In 1994, the U.S. Fish and Wildlife Service listed the silvery minnow as endangered. The fish once occupied 2,400 miles of the Rio Grande and one of its tributaries, the Pecos River. But during the early- to mid-20th century, federal agencies began damming, diverting and channelizing the Rio Grande to deliver water to farmers and cities and prevent flooding.

That work was incredibly effective, so effective that it transformed the river’s entire ecosystem. Spring floods no longer roared through the valley, creating a braided channel and leaving behind sediment and seeds; the water’s chemistry and temperature changed. The resulting combination of habitat loss, introduced species and declining water quality decimated the minnow, which needs shallow eddies and backwaters to survive.

By the time it was listed, the fish had disappeared from all but a 174-mile stretch of the Middle Rio Grande near Albuquerque. But the listing didn’t guarantee its recovery. The river remained fragmented by dams and diversions, and its waters were entirely claimed by people. New Mexico’s farmers and cities need water, and the state also has to send Texas an annual share. The Fish and Wildlife Service couldn’t upend nearly a century of water development just to assist a two-inch-long fish.  

Then, in 1996, about 90 miles of the Rio Grande south of Albuquerque dried up entirely — an unprecedented event, according to many. “It was really weird to watch this river just go dry,” recalls Christopher Hoagstrom, who was then an Albuquerque-based Fish and Wildlife biologist. That year, he and a few other biologists rode ATVs up and down the channel, stopping to pound t-posts into the mud and sand where pools remained as the river trickled to a halt. They checked the water daily for fish and tracked how quickly the pools evaporated.

“The fish would be so packed in these pools that when you’d (run a net) through it, you’d just be bumping fish,” he says — minnows, red shiners, flathead chub, catfish, carp, buffalo fish. Sometimes they’d whiz past a t-post that marked the site of a pool that had vanished from a day earlier. “I guess the vultures and raccoons came in, because you couldn’t even see a fish bone,” he says.

One evening after work, Hoagstrom and another biologist sat outside their office, feeling the weight of despair. The minnow was going extinct on their watch. “We said to ourselves, ‘We could collect eggs, bring them to the hatchery,’ ” he recalls. If they didn’t, they wondered, could they live with themselves if the fish blinked out? They decided they couldn’t. “But we knew we were giving up by doing this,” says Hoagstrom — giving up, that is, on the wild population.

Some biologists objected. Captive propagation would give water managers an easy out, allowing them to avoid keeping water in the river without losing the species altogether. “We wanted to be idealistic,” says Hoagstrom. He hoped Fish and Wildlife would require water managers to keep the river flowing for the fish, a move that would also contribute to the river’s health.

Instead, in 2003, the agency ignored its own biologists’ recommendations and issued a new policy that allowed water managers to dry the riverbed after June 15, when irrigation season begins. And even though it was supposed to be updated again in 2013, the agencies are still operating under that 12-year-old plan. “If we were idealistic,” Hoagstrom says now, “the silvery minnow would have been screwed.”

 

U.S. Army Corps of Engineers team members in the Albuquerque District use the dual-net seining process to collect silvery minnows and other fish in the Rio Grande in 2014. The district is part of a program to increase the number of silvery minnows in the river and improve their habitat.
Ronnie Schelby/Albuquerque District, USACE

Today, most of the Rio Grande’s minnows come from the Fish and Wildlife Service’s Southwestern Native Aquatic Resources and Recovery Center in Dexter, in southeastern New Mexico. Tucked against the Pecos River and surrounded by alfalfa fields and dairies, the center includes indoor and outdoor pools, a fish health center and a genetics laboratory. It consistently rears enough eggs that biologists can release hundreds of thousands of minnows each fall. “We’ve been making adjustments for 13 years,” says director Manuel Ulibarri, including improved spawning techniques and genetic testing on parents to ensure healthy offspring. “We’re getting to the point where it’s almost a cookbook. We have a recipe that works to meet the numbers.”

But the river’s minnow densities remain “extremely low.” When biologists monitored it in April, fewer than 20 of the more than 3,200 fish collected were silvery minnows. According to a recent report from American Southwest Ichthyological Researchers and Colorado State University, those low numbers show that current efforts aren’t “sufficiently buffering the population” against decline. For the fish to survive on its own in the wild again, the researchers concluded, the river must flow in the spring and summer.

But as it stands, the Rio Grande lacks rights to its own water. And even though the U.S. Bureau of Reclamation’s water managers are constantly trying to wring more water from the system for minnows, the river and the species that depend upon it come last in line. 

This year, for instance, after a dry winter, Reclamation determined in April that it couldn’t spare water from upstream reservoirs for a spring pulse of water, a temporary surge needed to trigger spawning. Federal, state and local partners hustled to devise a way to find a little more water. Then, in May, it rained and rained; Reclamation could release water after all. Biologists watched the water levels, checked temperatures and monitored for eggs.

The increased flows may have triggered spawning, says the BioPark’s Ward, but collecting eggs became impossible: The water was too deep, the flows in many places too dangerous. In the end, biologists ended up with few more than the roughly 10,000 eggs they had collected by mid-May. It marked another point on a downward trend: In 2013, they collected around 60,000 eggs; last year, only 13,000. And by early July, fish salvage crews were preparing to rescue minnows once again, depending on the summer’s monsoon rains.

 

Hoagstrom left Fish and Wildlife in 2002 and now works as a professor at Utah’s Weber State University.  He won’t criticize the work being done in New Mexico. But he wonders if rearing fish outside the river was a mistake. “The minnow can live in this sandy, harsh, hot, flowing water that’s only about this deep,” Hoagstrom says, measuring out six inches with his hands. “But it needs floods, it needs flowing water all the time, and it needs a lot of habitat. It needs a lot of things that don’t occur now.”

The problem isn’t the fish; it’s the river. Even in good years, there’s no longer enough water. But the changes necessary to protect the fish are big, challenging and expensive. They range from changing the crops farmers grow and the methods they use, to curbing urban sprawl and retooling infrastructure to capture and store summer rains — maybe even changing how the state administers water rights.   

Most of the Rio Grande’s native fish species have already disappeared. “The odds are, if it still rained all the time, if there weren’t drought, it would still be on the track to extinction,” Hoagstrom says. “The fact that the others are gone suggests that it’s just lagging behind. But nobody ever talks about that — that the Rio Grande is really destroyed from an ecological standpoint. And the more we forget about that, the easier it is.”

This story was funded in part by an Institute of Journalism and Natural Resources­ Frank Allen Field Reporting Award.

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