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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.
 The U.S. Fish and Wildlife Service team pulls seine nets through almost any pool left in the drying riverbed. The rescuers check each pool for silvery minnow. They throw back the other species of fish. The pools are often hot and poorly oxygenated. (Photo by Diana Cervantes for Source NM)
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.
 Silvery minnow are primarily found in a stretch of the Rio Grande between Cochiti Dam and Elephant Butte — if there’s enough river to support the fish. If some catastrophic event occurs, they’re a lot more vulnerable because it’s more likely to affect all of them, said Thomas Archdeacon, left. (Photo by Diana Cervantes for Source NM)
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.
 Some of the pools range in depth from a few feet to a few inches. Under the June sun, they rapidly shrink. Archdeacon noted that the pools were appearing earlier each year, and the river is drying faster. (Photo by Diana Cervantes for Source NM)
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.
 Lyle Thomas places a silvery minnow found in a pool into an oxygenated holding tank on the back of the carts. The fish are transported to better environments, but their survival rate is low, since the fish are often unhealthy from being in the pools. (Photo by Diana Cervantes for Source NM)
Dry beds
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