Combining the Trojan Y chromosome and daughterless carp eradication strategies

The Trojan Y chromosome (TYC) strategy and the daughterless carp (DC) strategy represent two autocidal genetic biocontrol methods for eliminating invasive fish by changing the sex ratio of the population. Each strategy is designed to reduce the number of females in a target population, ultimately leading to local extinction of the population. In the DC approach, the proportion of males in the population is increased as a result of introducing an autocidal fish containing a transgenic aromatase gene insertion into multiple autosome sites. In the TYC approach, matings of an autocidal fish containing two Y sex chromosomes results in an increased proportion of males in the population. A mathematical model based upon coupled ordinary differential equations was constructed to observe the effect of an autocidal fish with the combined genetic features of both strategies (TYCDC) on a target population. The model incorporated a fitness parameter associated with fish bearing aromatase inhibitor genes and for fish bearing two Y chromosomes. Under conditions where the fitness penalty of the autocidal fish was negligible, modeling results showed that a combined strategy produced a modest reduction in the time required for female eradication, and that fewer autocidal fish were required to achieve extinction. However, increasing the fitness penalty associated with the autocidal fish neutralized the benefits of the TYCDC strategy, and suggested that the effort and expense of a combined strategy may not be warranted if the fitness cost of the TYCDC autocidal fish is significant.