An endangered species of fish is making a comeback in southern Arizona.
The Gila topminnow had not been seen in the Santa Cruz River for a decade — until last month. Scientists credit treated wastewater for the fish's return to its native habitat.
For years, that stretch of the Santa Cruz has been the recipient of effluent discharged from the Nogales International Wastewater Treatment Plant near Nogales, Arizona. But when the plant underwent major upgrades in 2009, nitrogen, thick layers of algae and microorganisms began to clear up enough for more wildlife and plants to reemerge.
Ian Dowdy is with the conservation group the Sonoran Institute, which works on river restoration efforts with the state. He said this discovery of the minnow is an indication of how this riparian habitat continues to rebound and can be a lesson for other drying river systems in the West.
“By bringing reclaimed wastewater and improving its quality, we can actually maintain biological diversity in similar systems in the state and across the United States,” said Dowdy.
The minnow had been living in tributaries of the Santa Cruz and on the other side of the border, but Dowdy’s organization believes flooding washed the minnow down into this region of the river.
