Earth Notes: Silvery Minnow Rescues

Jul 4, 2018

Summers like this one, the Middle Rio Grande in New Mexico is a river without water. When it dries up, tiny fish become trapped in shrinking pools. But rescue missions are underway.  

A female silvery minnow
Credit Los Lunas Silvery Minnow Refugium

Just a few inches long, the Rio Grande silvery minnow has been listed as endangered since 1994. The once-abundant native fish is now confined to a stretch of less than 200 miles of the river.  

Every summer biologists with the U.S. Fish and Wildlife Service drive off-road vehicles loaded with fish tanks into the dry riverbed. They scoop up the minnows from doomed puddles and carry them to wetter parts of the river. Tens of thousands of the fish are trucked to safety this way. 

But this isn’t the only recovery effort in progress. Scientists at the City of Albuquerque’s BioPark net free-floating, transparent eggs out of the Rio Grande in May and place them in an aquaculture tank. The minnows are hatched and raised there in a donut-shaped “raceway” that flows like a real river.

In the Village of Los Lunas south of Albuquerque, biologists built an experimental refugium.  A winding stream spills into a series of ponds, meant to mimic the minnows’ natural habitat. Here, the young fish must find their own food and avoid predators like kingfishers and dragonflies. Those that succeed are released into the wild.

These rescue efforts have kept the silvery minnow from extinction—so far. But its long-term survival in the wild depends on water in the Rio Grande. By learning how to save this little fish, scientists hope to protect many more species that rely on a flowing desert river.