Eradicating Invasive Species Through Sex Reversal

An exotic species is a species that is not native to its current habitat and is known as invasive if it negatively impacts this habitat. There have been a variety of attempts to eradicate invasive species in different areas, but they have not been particularly successful. In an effort to find a better method for eradicating invasive fish species, Gutierrez and Teem proposed a method involving sex-reversal [2]. In 2001 it was discovered, in the Columbia River in the northwestern United States, that exposure to certain sex hormones can feminize XY fish, allowing them to reproduce [4]. Then when a feminized XY fish mates with a male XY fish, they can give birth to a YY fish, known as a supermale. Similarly, hormone exposure can feminize these YY supermales, allowing them to reproduce also. Gutierrez and Teem’s proposed eradication method involves the introduction of feminized supermales of an invasive species into a wild population. The feminized supermales will mate with the wild XY male fish and give birth to YY supermales. Thus there will be four different populations in this species: female XX, male XY, supermale YY, and the introduced feminized supermale YY. With these four populations, there are four different reproduction possibilities. The progeny from the mating of XX and XY is 1/2 XX and 1/2 XY, the mating of XY and the male YY produces 1/2 XY and 1/2 male YY, the mating of XX and male YY produces all XY progeny, and male YY and female YY mating produces only male YY. As the number of supermales and feminized supermales increases, the number of XX females born will decrease. The goal is to eventually eliminate all of the female fish so that when the addition of feminized supermales stops, the species will die out.