This research addresses both conventional pond culture and intensive indoor facility of walleye production that requires preventing the release of domesticated fish. Implementation of fish sterility (improved feed efficiency) and all-female (fast growth) production has resulted in nearly 30% cost reductions in related percids; therefore, it has the potential to enhance the economic value of cultured walleye for recreational stocking and food markets. Specifically, by securing all-female progeny and polyploidy (sterility), both improved growth rate and prevention of introgression of domesticated stocks with wild populations can be achieved. Results of this project will alleviate one of the main concerns of the general public, prevention of invasions of fertile fish from aquaculture. The importance of understanding the effects of environmental conditions (stress; hormonal regulation) on sex determination is magnified by the threat of climate change.
Walleye were spawned in 2021 as part of a NCRAC supported project, underwent experimental treatments for gynogenesis and hormonal sex reversal with methyltestosterone (Fig. 1). Their growth, survival, and sex ratio has been monitored. We validated genetic sex of gynogenetic walleye (produced with UV-irradiated yellow perch sperm, which produces non-viable hybrids) and gynogenetic individuals that were subjected to masculinization. Both groups produced sperm in January 2024 (Table 1). Validation of stress-related hypothesis of phenotypic sex-reversal in walleye by cortisol-induced masculinization and antagonistic effect of estradiol (E2) via dietary source is currently being developed. To test the viability and fertilizing ability of OSU walleye gynogens, sperm will be sent to Iowa DNR and Wisconsin DNR state hatcheries to fertilize wild walleye females and compare with their local walleye stocks in 2025.
One of the objectives of this presentation is to identify Midwestern State DNRs agencies (Wisconsin and Iowa already committed) that would be interested in collaborating in research and contribute financially with expected results in the domain of analysis of walleye ploidy (Farrell, Delomas et al. 2022), sex related sequences allowing to identify genome of individual fish and validate against phenotypical sex (including male sperm ducts functionality). This area of research is connected closely with their own state walleye hatchery management programs and addresses regional food security as well as the importance of walleye to Tribal nations.