Arizona Wildlife Conservation Strategy

Gila Topminnow: A Little Fish with Big Impacts

The tiny Gila topminnow, listed as endangered in 1967, has become something of a cause celeb in the Tucson area in part because of outreach efforts by AZGFD. Celebrated by art in public places, like the more charismatic and also endangered jaguar, the topminnow has returned to the Santa Cruz River after a ten year absence. The collaborative efforts that resulted in the topminnow’s return to Pima County waters has garnered extensive local news and social media coverage.

In October 2020, Tucson Mayor Regina Romero personally helped AZGFD place more than 500 Gila topminnow into the Santa Cruz River near downtown Tucson. This historic event marked the first time in 100 years that the species could be found in these waters. The publicized occasion was made possible by improved wastewater treatment by Tucson Water at its Santa Cruz River outflow.

“Tucson Water, as well as Pima County downstream, are to be commended for using best practices in the treatment of wastewater, which has made the return of Gila topminnow to the Santa Cruz possible,” AZGFD Regional Supervisor Raul Vega said then. 

But the Gila topminnow’s story is more than an example of successful collaborative conservation efforts. The tiny fish is also being put to work—thanks to its appetite. The Native Fish Program at AZGFD is working with our partners at Pima County to introduce Gila topminnow to abandoned properties with standing water, such as pools. The Gila topminnow is playing an important role by gobbling up mosquito larvae and helping to reduce mosquito populations around the city.