Commercial Application of Out-of-Season Spawning of Walleye (Sander vitreum)
Funded By: University of Wisconsin Sea Grant Institute
Walleye is recognized in the National Aquaculture Development Plan as a species with substantial aquaculture potential because of its high market value and limited supply from traditional commercial sources. The Freshwater Fish Marketing Corporation of Winnipeg, Canada, purchases 3.2 – 5.0 million kg of walleye each year, and then processes, packages, and markets them to the U.S. These walleyes are harvested irregularly during the year and must be processed and frozen under less than ideal conditions. Frozen walleye is then thawed and processed at facilities before being refrozen and stored for long time periods before they are consumed. This leads to problems of freezer burn and off-flavor.
WALLEYE RAISED IN RAS:
RAS cultured walleye can be harvested as needed and at a rate that can be handled by processors. They can then be distributed rapidly to end users, all of which results in a fresher, higher quality product that is consumed. The UWSP NADF has experienced substantial success over the past ten years raising walleye in recycle and aquaponic systems. By using specialized larval rearing systems, enhanced husbandry, indoor closed-loop production, and optimized starter diets we have been able to assemble systematic culture protocol that has advanced walleye food fish production to the point that a Wisconsin commercial walleye industry is emerging. There remains a limited number of bottlenecks for commercial walleye industry production in Wisconsin, with one of the most important being the out-of-season availability of walleye fry.
COMMERCIALIZATION OF WALLEYE:
The next step in commercializing production of walleye is to establish out-of-season breeding practices so that bio-secure walleye eggs, fry and juveniles can be available year-round. Domestication is the process of manipulating "wild" fish, so they are better suited for controlled environmental conditions. A key factor for domesticating fish and establishing a commercial industry, is to control the annual, synchronous reproductive cycle so that spawning occurs multiple times during the year. Once this critical domestication step is resolved, a commercial walleye industry can succeed in Wisconsin that can supply eggs, fry, juvenile and food-sized fish when needed by consumers, producers and natural resource agencies throughout the year.
Our project will conduct key commercial production spawning cycles using out-of-season spawning practices to control the reproductive cycle of walleye irrespective of the season. Through photothermal manipulation and hormonal spawning induction we will produce at least four reproductive cycles that will generate eggs, fry and juveniles at commercial production densities throughout the year; comparing fecundity, growth, survival and developmental milestones. A final domestication step is to make walleye eggs, fry, and juveniles available year-round so that the industry can become established and responsive to grow-out producer and consumer needs.
The overall project goal is to investigate an emerging species suitable for commercial food fish aquaculture in Wisconsin.
Specific objectives are to:
1) Compare out-of-season spawning cycles to produce viable walleye eggs in incubation systems to achieve optimal fecundity, development and survival
2) Investigate the influence of photoperiod, thermal and hormonal manipulation on spawning walleye to optimize the production of viable eggs and fry based on fecundity, development, survival, and growth milestones
3) Compare the continued grow-out of out-of-season produced walleye under controlled environment conditions (RAS) while demonstrating and transferring information to Wisconsin's aquaculture industry through outreach activities.