Converting Pond-Reared Walleye Fingerlings to Formulated Feeds: Effects of Diet, Temperature, and Stocking Density

Abstract

Two feeds, two tempratures, and several stocking densities were evaluated to determine their influence on the success of training 50- to 60-day-old (2.2-2.6 g), pond-reared walleye. Stizostedion vitreum, fingerlings to formulated feed in intensive culture. The training period was 29-days and three cohorts (1987, 1988 and 1989) of pond-reared fish were used. In the 1987 trials, at an average temperature of 20.5°C, survival was not different between fish fed a hard, granular feed, W-16, the coolwater diet developed by the U.S. Fish and Wildlife Service, and those fed BioMoist Grower, a commercial, closed-formula, semimoist (soft) feed. However, young walleye grew faster (mm/day) on the BioMoist feed, but fish fed the W-16 feed, had a higher condition factor (K). in 1988, survival of fish reared at 20.1°C and 24.9°C was similar, 76 and 80%, respectively; however, in 1989, the difference in survival at 20.8°C and 25.2°C was significant (68 and 85%, respectively). With the exception of poor performance for one midrange stocking density (2.29 g/L) for the 1989 cohort, stocking density (0.87-3.21 g/L) had no effect on survival in any year. With one exception, the 2.29 g/L density category, there were no statistically significant itneractions between stocking density and temperature. In all years, most mortality was due to columnaris disease, which mailnly occurred during the first eight days of training trial; in most treatment groups, mortality stabilized for the rest of the training interval. Disease seemed to result from the stress of transportation and handling. Walleye are said to be "inherently" cannibalistic, but overall, cannibalism was a minor problem (3.2 to 6.9% of mortality); however, it was more acceptable stock densities, temperature, options for feeding, and other factors needed to successfully train pond-reared walleye to formulated feed.