As part of an ongoing project, primarily funded by the University of Wisconsin Sea Grant Institute, Malison and his colleagues have developed methods to produce all-female populations of walleye and yellow perch. The process involves adding a form of the male hormone testosterone to the diet of young female fish. When these females reach maturity, they produce sperm, which is used to fertilize normal eggs. Since the sperm harbor female chromosomes, all the offspring from this pairing will be female.