Lower Colorado Region Partners to Fight Mosquitos in Arizona

An Endangered Fish Fighting Back

The Gila Topminnow
The Gila Topminnow
A small minnow, not much larger than a paper clip, is the newest weapon in the fight against mosquito borne diseases in Pima County, Arizona. The Gila Topminnow, a Federally protected fish that feeds on plants and small invertebrates, like aquatic mosquito larvae, is now serving Pima County as a vector control agent.

The Bureau of Reclamation’s Gila River Basin Native Fish Conservation Program, partnered with Pima County, the Arizona Game and Fish Department, and the U.S. Fish and Wildlife Service to secure a holding tank for the County to rear this endangered fish. The County will place the newly acquired Gila Topminnow into abandoned swimming pools, fountains, backyard ponds, and other locations where mosquitoes breed. The County worked with state and federal wildlife agencies to secure the topminnow population as well as acquire the necessary compliance to make this a reality.

This is not the first time fish have been used for vector control. In fact, it is a regular practice to use mosquitofish to control mosquito populations. While this may be a good thing from a vector control standpoint, mosquitofish are not native to the Gila River basin and are one of the leading threats to the decline of the Gila Topminnow through predation and competition for space and food. Using Gila Topminnow rather than a more easily acquired mosquitofish for vector control is a step in the right direction. With this method, the Region’s Phoenix Area office is supporting Pima County and its partners by not only reducing local health threats such as Zika and West Nile virus, but also serving to reduce the threat of nonnative mosquitofish that otherwise might be used for vector control.

Historically, Gila Topminnow were the most abundant species in the Gila River basin from western New Mexico to southern Arizona. Loss of habitat and introduction of nonnative fish have led to its severe decline. Partnerships like the one that made this happen and a County willing to think outside of the box provide a glimmer of hope that recovery of this species is possible.

Published on June 01, 2017