The Rio Grande silvery minnow was once the most abundant fish in the entire Rio Grande -- a river which stretches from the mountains of southern Colorado through New Mexico, and is the border between Texas and Mexico from El Paso to the Gulf of Mexico. 

A "pelagic" spawner, silvery minnow eggs are semi-buoyant and float downstream with the current, until caught in eddies where the young minnow mature.  Silvery minnows thus swim upstream to spawn; and the migrate up and down the river searching for food and suitable habitat.  This ability to travel along the Rio Grande allowed the silvery minnow to survive low water periods historically.

Now the Rio Grande is heavily dammed and diverted for irrigated agriculture.  The dams prevent the silvery minnow from migrating along the river as it used to; and the diversions dry up the Rio Grande for long stretches.  As a result, populations have plummeted; and the silvery minnow is now confined to a stretch of the Rio Grande totalling less than 200 miles in the vicinity of Albuquerque.

The Rio Grande silvery minnow was listed as an "endangered" species by US Fish and Wildlife Service in 1994.  See 59 Fed. Reg. 36988 (7/20/94).  Nearly eliminated by drought periods and excessive water diversions during the late 1990's, the silvery minnow continues to barely survive in the Rio Grande today.  

Reforming water use, improving dam operations, and reestablishing minnow populations in other parts of the Rio Grande are essential to the species' survival.