“The Apache trout and roundtail chub that are native to Arizona’s West Fork Black River have long struggled to compete against invasive brook trout (Salvelinus fontinalis). So it may seem strange that biologists are dumping even more hatchery-raised brook trout into the river. But these new trout are bred to have a genetic quirk designed to doom the population.

Sometimes called supermales or Trojan YY males, they have two Y chromosomes instead of one. When supermales mate with female wild trout, the offspring are all male—eventually producing a population that consists only of elderly bachelors. In the Black River, the population last year climbed to 61% male—' good sign,' says Zachary Beard, the Arizona Game and Fish Department’s statewide native aquatics program manager. And in July, scientists showed supermales had eradicated brook trout from two streams in Idaho.

'It’s really exciting that they were able to show that [supermales] worked,' says conservation geneticist Thaïs Bernos of the University of Vermont. 'It’s a tool that will become very useful.' And it likely won’t be limited to brook trout; researchers are now developing supermales to combat an array of invasive fish that pose a serious threat to native species.”

From Science.