Rescuing silvery minnows like ‘slapping a Band-Aid on a severed limb’

SOCORRO COUNTY, N.M. — Four people walk the streambed, combing the pools in Socorro County’s San Acacia Reach. Two wade thigh-deep in the bank crook, a seine net strung between them, and tug it through the water. Another calls out temperatures and measures the pool. The fourth jots it down in a notebook.

At the edge of the pool, the net is suddenly boiling with violent wriggling and thrashing. Mallory Boro from the U.S. Fish and Wildlife Service gently grasps a small fish with one deft flick of a hand. An endangered silvery minnow.

The minnow is placed in a five-gallon bucket and then moved to an oxygenated rescue tank on the back of an all-terrain vehicle. Then, onward to the next pool to do it all again. There are miles of riverbed left to go.

This is a fish rescue on the Rio Grande. And the people doing it know it’s not enough.

“This is like slapping a Band-Aid on a severed limb,” said Thomas Archdeacon, who has led the silvery minnow recovery project for the U.S. Fish and Wildlife Service in Albuquerque, N.M., for the past decade.

These rescues require a lot of work, but even so, the fish are often in poor health from being in shallow, hot pools with little oxygen. Or they are sickened by other dead and rotting fish left behind when the water recedes.

“The ones that we rescue don’t survive very well. We’re getting between a 5% and 15% survival rate, which is bad,” he said. “Healthy fish have an 80% to 100% survival rate.”

Archdeacon drops his posture, taking a moment to rest against the ATV. He is an earnest speaker, lent gravitas by the touch of gray in his red hair. He has been studying and publishing research about the fish for nearly 15 years — most of his career.

Between 18 and 20 miles of the river dried in the San Acacia Reach overnight in mid-June, pushing the fish rescue crew to work punishing hours. The pools were smaller and drying faster than usual for June.

More effort has to go to restoring the habitat that fish could survive in, and securing water in the river, he said.

“Eventually, we’re trying to take the emphasis off of the fish rescue, because it’s not effective conservation,” he said, running a hand across his face as the day creeps above 90 degrees.

Spawning between dams

The silvery minnow is not a charismatic species. The nondescript fish is green to yellow on top, a cream underbelly usually no more than 4 inches long, with small eyes and a small mouth. It’s short-lived, estimated to survive just over one year or up to two years in the wild, and four years in captivity.

Shoals of minnows used to swim nearly 3,000 miles of the Rio Grande’s length from the Gulf of Mexico to Española, N.M., and along much of the Pecos River.

They are unique in one aspect: Unlike most freshwater fish, the silvery minnow directly spawns into the water in the spring, and then the fertilized eggs slip downstream. This technique, called pelagic broadcasting, is much more common for marine creatures. The silvery minnow is the last of five species that spawn this way living in the Rio Grande. One is extinct entirely. The others survive in different rivers, but no longer in the Rio Grande.

In earlier times, shallow wetlands emerged at the river’s bend. In slow eddies and silty bottoms, the silvery minnow was prolific. The species follows the river’s rhythms, waiting to spawn when the spike of snowmelt pulses.

But federal and local irrigation projects straightened the river, making it deeper and faster. They removed the bump of snowmelt, storing it in reservoirs for crops. The construction of Elephant Butte and other dams prevented fish from moving upstream. Eggs and larvae drift downstream to face predators or cold water in Elephant Butte. The river carries others into irrigation ditches or dry streambeds, where fish may hatch, but there is little chance for returning to the river to spawn.

In 1994, after years of steep declines, the silvery minnow was listed as endangered at the federal level.

Now, the fish are primarily found in a stretch of river between Cochiti Dam and Elephant Butte — if there’s enough river to support silvery minnow.

“If some catastrophic event occurs, they’re a lot more vulnerable because it’s more likely to affect all of them,” Archdeacon said.

For 25 years, the San Acacia Reach has dried nearly every summer when farmers divert water for crops, according to documentation held by the Rio Grande Compact Commission.

Archdeacon said he doesn’t have any answers as to why the silvery minnow population has better reproduction and recruitment chances in the reach, compared with upstream in Albuquerque, where the river has only dried once in the last 40 years — in the summer of 2022.

“My guess is that the eggs float downstream, and the channel is wider — more sand bed — and shallower, which is just better for reproduction,” he said.

Drought complicates recovery efforts on all sides. In a good year like 2017, the fish population boomed into the millions. But only a tiny number lasts long enough to continue the next generation. And in lousy years, which are more frequent, that dwindling number of spawners only shrinks. In 2018 and again in 2022, the river dried before the fish could spawn.

Even when thousands of fish spawn simultaneously, only a few successfully carry on to the next generations.

Federal agencies partnered with hatcheries and the ABQ BioPark to breed other silvery minnows, in the tens of thousands to hundreds of thousands, both for release into the wild and as a bank against inbreeding when wild populations crash.

“Genetically speaking, it’s keeping them from going down a hole they can’t dig themselves out of,” Archdeacon said.

But dumping hatchery fish into the Rio Grande is not a silver bullet. Recovery means a wild, sustainable population, which Archdeacon added would require “serious large-scale habitat restoration” and sufficient water flows to spawn.

If 1 million to 2 million fish were upstream and successfully spawning each spring, he estimated, then fish rescue may be worth it.

But that’s not the reality.

In 2022, early drying wiped out egg collection efforts. With the 2020 and 2021 generations reaching the end of their lifespan, the 2023 generation will be vital for keeping the hatchery populations alive.

“But there’s also nothing that prevents this from happening again,” Archdeacon said.

Dry beds 

Nothing dies quietly in the riverbed. Dozens of blue catfish, golden green smallmouth buffalo and red shiners grow brown as they writhe in the silt, seeking a pool. Some red remains as their gill slits flare, and they twist and slam their bodies into the mud.

Their moments of frantic slapping stretch into long, excruciating minutes. It takes nearly an hour before some of the larger fish heave their last breath.

When the pools are large enough, maybe between ankle- and knee-deep, the team can throw the fish back in to survive in shrinking pools. But when the pools shrink to just the barest puddle, it means throwing the fish that aren’t silvery minnows out into the mud.

Archdeacon cradles a native smallmouth buffalo. “If the river wasn’t dry, nothing would eat them,” he said, putting it onto the ground. “I’d guess this one is about 10-years-old.”

The minnow, unlike the other fish trapped in the pools, is on the federal list of endangered species — that’s why there’s a team to save them.

Human choice is central to what’s happening here, Archdeacon said, just as people make decisions to use water elsewhere, and this dry bed is a consequence.

“You’re choosing people over fish,” he said. “You cannot paint this into a rosy picture. If you’ve been out here, it’s not good.”

Some of the fish rescuers said they’ve become somewhat desensitized to the mass death of other fish. They have a job to do.

Still, it doesn’t really get easy, either.

“I think about this 365 days a year,” Archdeacon said. “I can’t sleep at night. It’s pretty bad.”

Driving out of the sand bed of San Acacia, away from fish gasping in the riverbed, irrigation canals criss-cross under roadways, full and glistening in the sun. Fields of green alfalfa zip by, watered by pivot sprinklers.

Little fish, big controversy

The silvery minnow has been central to a slew of lawsuits against the federal government, at district and appellate levels.

Out of a case brought jointly by New Mexico, irrigation districts and conservation groups, a 10th Circuit Appeals ruling in 1999 found that top U.S. Fish and Wildlife officials at the time had not followed procedures in securing habitat for the fish. Three years later, the same court found the agency was dragging its feet in providing needed documentation, writing: “These delays and irrational decisions come at the expense of the silvery minnow, officially endangered for nearly eight years.”

More years of litigation resulted in a 2020 federal appeals court decision upholding a lower court’s determination that the U.S. Army Corps of Engineers was not allowed to provide additional water for endangered species and was not required to consult with the U.S. Fish and Wildlife Service to change its practices.

In 2021, WildEarth Guardians — a western conservation nonprofit headquartered in Santa Fe — filed a notice of intent to sue the U.S. government over a 10-year plan between agencies to ensure they wouldn’t harm endangered species.

That plan, set up just a few years before the lawsuit, was the result of a consultation on a series of reclamation projects and water operations in habitats for the silvery minnow, Southwestern willow flycatcher and yellow-billed cuckoo — all species with federal protections in the Middle Rio Grande.

The nonprofit wrote a letter addressed to federal agencies and New Mexico state department leaders, announcing their intention to sue:

“We hope that this warning (both the legal notice and the dire conditions on the river) will provide water managers, and quite frankly all people, an incentive to rethink water management as it has existed this past century and chart a new course for this dying river,” the letter said. “The Rio Grande is too valuable to lose.”

After talks and negotiations, further legal action is being taken.

In late November 2022, WildEarth Guardians filed a lawsuit in federal District Court, alleging that the U.S. Fish and Wildlife Service and Bureau of Reclamation violated the Endangered Species Act with the 10-year plan.

U.S. Fish and Wildlife found that the bureau did not jeopardize any endangered species in its 2016 plan. WildEarth Guardians alleges that the decision was “arbitrary,” relies on “vague, uncertain and unenforceable” conservation measures, and failed to consider climate change’s impact.

The current plan wouldn’t meaningfully recover species, the nonprofit said.

WildEarth Guardians asked the court to toss out the 10-year plan and require the agencies to reexamine projects and operations on the Rio Grande.

The silvery minnow’s population is worse off than when it was listed three decades ago, said Daniel Timmons, the river programs director and Rio Grande waterkeeper for WildEarth Guardians.

“Actually limiting the amount of water that’s being taken out of the river in order to make sure there’s enough water left for fish is an action that the federal government has continued to refuse to do,” Timmons said.

Federal management of dams, diversions and depletions is the primary threat that removes water from the river ecosystem, he said.

“It’s not just about the silvery minnow. It’s about the river as a whole,” Timmons said. “That’s the piece that the federal government to date has really failed to grasp, is the importance of the species as an indicator of an entire river system in crisis and collapse.” team can identify if the silvery minnow came from a hatchery fish by color-coded tattoos. (Photo by Diana Cervantes for Source NM)