ONE OF TWO NATIVE TROUT IN ARIZONA
The Gila trout (Oncorhynchus gilae), one of two native trout species in Arizona (the other is Apache trout O. apache – Apache Trout Recovery), is one of the rarest trout species in the United States. Historically, the fish was native to the San Francisco, Verde, Gila, and Agua Fria River drainages in New Mexico and Arizona. By the 1950s, however, its range was reduced to only four streams in the Gila River headwaters in New Mexico, and none were found in Arizona. The Gila trout was listed as federally endangered in 1967, and reclassified as threatened in 2006 after efforts to restore populations were successful.
Currently in New Mexico, Gila trout have been restored to a number of streams in the headwaters of the Gila River and San Francisco drainages. In Arizona, Gila trout have been restored to one stream in the Blue River drainage, two streams in the middle Gila River drainage, and one stream in the Agua Fria drainage, and more streams are being considered for future Gila trout reintroductions.
Hybridization with non-native rainbow trout is a major cause for this historical decline and continued imperilment of Gila trout. Stocking of rainbow trout within the historical range of Gila trout began in the early 1900’s, and they have become naturalized throughout the range of Gila trout. Hybridization remains a prominent threat because if results in the loss of the unique genetic identity of the species, which represents its evolutionary history and local adaptation to the environments it inhabits. Unless natural barriers are present, the installation of artificial barriers is a necessary component for both Gila trout and Apache trout recovery to maintain isolation from non-native salmonids. Continuous monitoring of the genetic structure of pure Gila trout populations is necessary to ensure maintenance of the genetic purity of recovery populations by rapidly identifying compromised populations.
Gila trout evolved to withstand the environmental conditions within its range, and small populations have persisted throughout history in small headwater streams where they are isolated from non-native trout. However, those populations, as well as restored populations in headwater streams, may be subject to risk or extirpation from stochastic events such as drought, wildfire, and post-fire flooding. These events appear to be on the rise, making species such as Gila trout and Apache trout especially vulnerable.
As Gila trout recovery streams are established and meet necessary population criteria to withstand limited angling use, they may be opened to angling for the public in the future. Currently, all Gila trout recovery streams in Arizona are closed to angling. However, Gila trout in Frye Mesa Reservoir in southeastern Arizona can be angled, with a one fish limit. For information on fishing for Gila trout in Arizona, and the associated regulations. There are also opportunities in New Mexico to catch Gila trout during a limited angling season with catch-and-release only regulations.
Julie Meka Carter
Native Trout Conservation Coordinator
Arizona Game and Fish Department, Fisheries Branch
5000 W. Carefree Highway
Phoenix, AZ 85086-5000