Fingerling Walleyes in One Growing Season for Stock Enhancement

Production of fingerling walleyes Sander vitreus in the United States and Canada from 1984 to 2006 nearly doubled from 21.9 million in 1984 to 40.7 million in 2006, and there was a four-fold increase in jurisdictions involved in walleye stocking between 1984 and 2006. In the U.S., 34 states had stocked walleyes in 2006. Among the state governmental hatcheries, there are several that have production capabilities at a single hatchery in excess of a million fingerlings, mostly 38–51-mm (1.5–2.0 in), but also fingerlings 100-150 mm (4-6 in) total length. The Iowa Department of Natural Resources (IDNR) Rathbun Fish Hatchery (RFH) annually produces about 170,000 advanced (200-250 mm) walleye fingerlings. These advanced fingerlings are highly desired by management biologists because of their high post-stocking survival. They are stocked in broodstock lakes and at other locations throughout Iowa to improve recreational fisheries. Nearly thirty years of systematic research has been undertaken to overcome critical constraints on all stages of walleye culture. Tailoring our culture system to accommodate walleye's environmental preferences minimized their cannibalistic tendencies resulting in improved growth and survival. Survival is now 70% from fry to a 225-250 mm (9-10 inch) fall fingerling. Currently, all advanced walleye fingerlings produced at RFH are from a tandem pond and tank method capable of producing walleye in excess of 230 mm in a five-month period. After a 35-day period of fry culture in ponds, fish are habituated to manufactured feed in a unique indoor environment with covered tanks and in-tank lights. Thereafter, they are moved to outdoor tanks and reared entirely on pelleted feed. A summary of these techniques is presented as well as advice for others about to embark in rearing large walleye.