Potential for Gila Trout egg stocking as a successful repatriation tool

Authors: Zachary Beard

Year: 2019

Abstract

Gila Trout, Oncorhynchus gilae, is endemic to streams above 1524 m in the Gila River basin of Arizona and New Mexico. Gila Trout were originally listed as endangered under the Endangered Species Act in 1973 and were down listed to threatened in 2006. One of the actions required to recover and delist Gila Trout is their repatriation into streams throughout their historic range. Currently, the most common way to repatriate Gila Trout is to stock Gila Trout that are 6-8 months old. This method is largely successful, but it has its disadvantages. Many Gila Trout recovery streams are remote and are difficult to access. As a result, a large amount of effort is required to carry 250 to 500 Gila Trout in to stock in a stream. One alternative to fish stocking may be the stocking of fertilized eggs into artificial redds built in the stream. We tried this approach on two Arizona Gila Trout recovery streams, Grapevine and Frye Creeks. We stocked 19,000 Gila Trout eggs at Grapevine Creek and 24,000 Gila Trout eggs at Frye Creek. Visual surveys one month after stocking found good survival of Gila Trout at Grapevine Creek, but no survival at Frye Creek. Stocking eggs may provide a method for repatriating Gila Trout eggs that requires less manpower and reduces the cost of raising fish.