Sex control and ploidy manipulations in yellow perch (Perca flavescens) and walleye (Stizostedion vitreum)

In both yellow perch (Perca flavescens) and walleye (Stizostedion vitreum), females grow significantly faster and reach a larger ultimate size than males. In addition, reproductive development in both of these species can have a significant negative impact on somatic growth and fillet yield. Accordingly, methods for producing monosex female populations and for inducing sterility, have important potential applications for both commercial fish culture and fisheries management. Of the several available methods for producing monosex female populations in fishes (such as yellow perch and walleye) in which females are homogametic, the preferred method (described herein) may be to treat juveniles with androgens to induce phenotypic sex inversion of genetic females, and to subsequently use sperm from these females to fertilize normal eggs. Initial efforts at inducing sterility focused on the direct use of either heat or hydrostatic pressure shocks to produce triploid yellow perch and walleye. The gonadal development of triploid yellow perch and walleye of both sexes is retarded compared to that of diploids, and triploid yellow perch can have higher fillet yields than diploids. The direct use of heat and pressure shocks to induce triploidy in yellow perch, however, has negative effects on growth that are independent of ploidy status. One way to circumvent this problem is to produce triploids by crossing fertile tetraploids with diploids. To date, methods of producing viable tetraploids (beyond the larval stage) have been developed for yellow perch but not for walleye.