Brook trout are marvelous and beautiful fish (as shown in this brook trout flank here), but they can be harmful to other endangered trout populations when they exist in non-native drainages. (Joshua Bergan photo)
March 11, 2022
By Fly Fisherman Staff
A ground-breaking method for eliminating invasive brook trout is being explored in some remote streams throughout the American West. Researchers in New Mexico, Nevada, Idaho, Washington, and Oregon are looking into whether hatchery-bred male brook trout (Salvelinus fontinalis ) that are manipulated to have two Y chromosomes could safely solve a major problem in many Western drainages.
The idea is that these so-called “trojan” brook trout released into drainages where brook trout have become dominant over a native trout, like cutthroats. The brookies, which seem to have no side effects from the genetic manipulation, would then theoretically breed with the non-native but wild female brook trout. Because these males have YY chromosomes (rather than the normal XY chromosomes), breeding with typical XX females will almost always result in the offspring being normal XY males. After a period of time with only male progeny, the population will die out from lack of natural reproduction, and the unaffected native fish can repopulate the creek.
The best-known of these experiments has occurred on New Mexico’s Vermejo Park Ranch reserve and on several creeks in the upper part of Idaho’s Big Lost River drainage .
The genetically-altered-fish-stocking projects are often implemented in conjunction with electroshocking removal of brook trout. Researchers are cautiously optimistic that the combination of tactics could be a game-changer in the future of endangered native cutthroat trout populations.
Similar experiments have been done on invasive mosquito populations in Florida and California .
Innovative methods like this could reduce or eliminate the need for controversial half-life poison treatments like rotenone , which kills all fish in the affected area. But bioengineering also raises other ethical questions and unknowns.
Results of these experiments are yet to be seen, but inital observations are promising. Estimates are that it could take 10 years or more to know if these experiments have made dents in invasive brook trout populations.
Read more about the potential implications, ethics, and ironies of using "trojan" brook trout here.
