Western Division Project Spotlight: Evaluating YY Male Technology for Non-native Brook Trout Control in New Mexico
By Jill Wick, FMS Western Division Representative and Native Fish Program Manager with the New Mexico Department of Game and Fish
Non-native fishes can be the primary threat to many native fish species, yet there are few tools available to fisheries managers to control them. The New Mexico Department of Game and Fish has partnered with New Mexico State University (NMSU), Idaho Department of Fish and Game (IDFG), and U.S. Fish and Wildlife Service to develop a method to eradicate non-native Brook Trout Salvelinus fontinalis from waters that currently have or could potentially sustain native Rio Grande Cutthroat Trout Oncorhynchus clarkii virginalis. The method uses YY Male technology, developed by IDFG, where male Brook Trout are produced with two Y chromosomes and stocked into streams with wild Brook Trout. In theory, this method can skew the sex ratio toward 100% males until the population collapses.
New Mexico Department of Game and Fish has coordinated graduate research with NMSU on this project since 2018, and the results have been promising. In the study waters, wild Brook trout were removed and replaced with YY male Brook Trout and fin clips collected to determine sex and YY male parentage. Researchers determined that stocked YY male Brook Trout have high survival and are successfully spawning with wild females. In most of the study streams, the young-of-year populations of Brook Trout consist of 75% males or higher after just three years of stocking. This change in sex ratios towards male dominance indicates the method’s potential effectiveness that could lead to the suppression and eventual local eradication of non-native Brook Trout populations, aligning with management goals for the conservation of native fish species. Research is ongoing, with continued removals, stocking, monitoring, and analysis to fully assess the efficacy of this innovative approach.
New Mexico State University graduate researchers conducting population estimates on a Brook Trout population in New Mexico. Photo by Breanna Graves.
