PRODUCTION OF THE GYNOGENETIC FEMALE WALLEYE Sander vitreus AND INDUCTION OF SEX REVERSAL WITH METHYLTESTOSTERONE

Three meiotic gynogen families of walleye (Sander vitreus) were obtained via pressure shock in April 2018. We attempted hormonal sex reversal to produce "neomales" via feeding methyltestosterone (MT)-containing diet to both gynogenetic and control fish. The final objective of the project is to produce all-female sterile triploid fish. Fish from each family were fin-clipped and combined to "common garden" design (four 400L tanks) where they were fed MT- or Control-diets for 50 days and then PIT-tagged and fed the same commercial diets (Skretting USA). Survival and growth have been recorded throughout rearing. Fish were measured and PIT-tagged in September 2018 (140-147 dpf) and then measured in January 2019 (294 dpf).  In October 2019 (544 dpf), all surviving fish were measured and combined to a single 400L tank. Mean weights of each treatment group across the three families, are presented in Table 1. Resulting sex ratios of MT-treated gynogen and control fish will be examined histologically at the advanced stage of gametogenesis at age-1+. Preliminary data indicate sexual maturation of females preceding that of males (Figure 1).