Rio Grande Silvery Minnow's Plight a Marker for Conservation
by Stewart Jacks
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If you need a reminder that the Earth is bound by stone, look no further than the Sandia and Manzano mountains in central New Mexico. Born of what must have been violent tremors, the Rio Grande slices down a natural rift left behind by massive movements of gigantic plates of planet Earth that produced these majestic mountains. Where the southern Rockies end, these distinct mountains emerge. From where I live in Placitas, New Mexico, all the way to El Paso, Texas, the west face of a long chain of dry crags reveals the past.
In these tilted wedges, the remains of sea-dwelling creatures swim forever entombed in limestone, now 10,000 feet above sea level. Along this front of sandy mountains, few people live. Night skies are inky black and you feel you can still reach out and touch the cosmos rarely concealed by clouds. No clouds—no rain. The sky governs fate in the American Southwest.
The Rio Grande, as grand as it is, is not the river it once was. Despite the remoteness and sparse population, the river has been thoroughly humanized by command of its water. Rio Bravo del Norte, as the river is called in Mexico, has lost its bravado. It is wild and turbulent no more. A river that once flushed with spring snowmelt and summer freshets—pulses of water that told native minnows “it’s time to spawn”—has been weakened by manmade structures and diversions.
A river wide and braided that carved new paths under its own power as rivers are in the habit of doing, is now rather oddly perched above its own floodplain. Under the summer heat, sun and sand may soak it up leaving cakes of mud and pools soon to pass. Fresh sodden spring sediment rich with ripe cottonwood seeds that regenerate mosaics of riparian woodlands are historic artifacts, as prickly water-sucking non-native trees now dominate the depleted river’s rigid edge.
The Rio Grande still has water and fish need water—that’s a given. But good habitat for fish is much more than just water. And perhaps that’s most readily apparent in the plight of the Rio Grande silvery minnow, an endangered species that hangs on in a mere vestige of its once-expansive range.
The minnow that shines like sterling is as much New Mexican as are the mountains that frame what is left of its habitat. To thrive, the minnow needs a mix of slow-moving shallow pools as nursery habitats and steady mainstream flows to grow and spawn to maturity. Until there is enough suitable habitat, the U.S. Fish and Wildlife Service must help fill in the gaps.
The USFWS Southwest Region has committed many resources in partnership with the National Park Service and Bureau of Reclamation. Our Texas and New Mexico Fish and Wildlife Conservation Offices lead with monitoring and population assessments and direct future stocking endeavors. Field biologists have even saved Rio Grande silvery minnows from drying pools in summers past, when there were no river flows. They have collected and delivered brood fish for culturing next-generation minnows at the Southwestern Native Aquatic Resource and Recovery Center in Dexter, New Mexico, and Uvalde National Fish Hatchery in Texas. And they are optimistic that the minnow’s current range is expanding in Big Bend National Park.
The challenge ahead is huge. Captive-rearing this fish now helps buy some time to figure out what we need to do to create viable habitat in nature. Importantly, the silvery minnow’s situation is a marker for a larger conservation concern brought about by a river fully controlled by humans. Like the stalwart mountains that remain despite shifting sands, it’s our job to ensure that this piece of our natural heritage persists into the future.
Stewart Jacks is the Assistant Regional Director for Fish and Aquatic Conservation in the U.S. Fish and Wildlife Service’s Southwest Region and can be reached at Stewart_Jacks@fws.gov.
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