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Development of Trojan Y technology to control invasive fishes in the Greater Everglades

canal bank in Big Cypress National Preserve
Project Investigator: Pam Schofield

Project Personnel: Margaret Hunter, Darren Pecora, Jessica Schulte

Project Start Date: 2009 End Date: 2015

Recent Funding: (FY14) USGS GE PES, (FY13) USGS GE PES, (FY12) USGS GE PES, (FY10) USGS GE PES


Our objective is to develop the utility of this approach and test its applicability in a real-world setting. To do this, two broad phases must be accomplished: Phase 1) YY females must be developed in the laboratory, then Phase 2) their interaction with other individuals and the population consequences of these must be assessed.

Within Florida, dozens of foreign non-native fishes have established self-sustaining populations. There is concern that these introduced species could negatively affect native communities by predation, competition, or by serving as vectors for disease. Once a non-native fish has become established, there are almost no methods available to eradicate it or control its population size. New technologies must be developed to control non-native species, and help stop their spread. In this project, we are investigating the applicability of a theoretical model of invasive species control using Trojan Y sex chromosomes.

The Trojan Y technique of population control for invasive species was originally described by Gutierrez and Teem (2006) and consists of adding sex-reversed females containing two Y chromosomes (YY females) to a wild population to skew the sex ratio of subsequent generations to contain an increasing number of males (i.e., fewer and fewer females in each generation). The gradual reduction in females may lead to eventual extinction of the population. The potential of this technique for eradicating or controlling non-native species has been much-discussed and promoted (e.g., Cotton and Wedekind 2007; Teem et al. 2013; Thresher et al. 2013). However, until this project, no one has attempted to move beyond theory into practical application. The development of this technique requires several years of experimentation and exploration. Our project is the first in the world to attempt to adapt Trojan Y technology to a living model.

Trojan Y is favored over other techniques (e.g., genetic engineering) for the following reasons:

  • It is kinder on the environment than poisoning, which kills all (or most) species, including natives. With Trojan Y, only the target species is affected.
  • It is safer than genetic modification, because no genetically engineered genes are being transferred to subsequent generations.
  • It is reversible. If the influx of Trojan Y fish into the environment is stopped (before the population is extinct) the effect will be stopped in a few generations.
  • It is flexible. The strength of the effect is based on the proportion of treated individuals added. So it can be used for anything from mild control to complete eradication.
  • Does not require massive population influxes, as with sterile male techniques. A one-time introduction of a small number of YY females (ca. 3% of the population size) can skew the population towards males for several generations.

To date, this theoretical construct has never been demonstrated with a population of organisms.

Cotton, S. and C. Wedekind. 2007. Control of introduced species using Trojan sex chromosomes. TRENDS in Ecology and Evolution 22: 441-443.

Gutierrez, J. B. and J. L. Teem. 2006. A model describing the effect of sex-reversed YY fish in an established wild population: The use of a Trojan Y chromosome to cause extinction of an introduced exotic species. Journal of Theoretical Biology 241: 333-341.

Teem, J. L., J. B. Gutierrez and R. D. Parshad. 2013. A comparison of the Trojan Y chromosome and daughterless carp eradication strategies. Biological Invasions 10.1007/s10530-013-0475-2.

Thresher, R. E., K. Hayes, N. J. Bax, J. Teem, T. J. Benfey, F. Gould. 2013. Genetic control of invasive fish: technological options and its role in integrated pest management. Biological Invasions 10.1007/s10530-013-0477-0.

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