Effects of Fertilization and of Fry Stocking Density on Pond Production of Fingerling Walleye,Stizostedion vitreum

The influence of fertilization and of fry stocking density on production of fingering walleye, Stizostedion vitreum, was evaluated in earthen ponds at North Platte State Fish Hatchery, North Platte, Nebraska. In 1990, five 0.4-ha ponds were fertilized with alfalfa pellets, and five were fertilized with soybean meal; four unfertilized ponds served as controls. All ponds were stocked with D2 (Dl = the day at hatch) walleye fry at 250.000ha. Differences in yield, number of fingerlings harvested, mean length, and mean weight amone treatments were not statistically significant (P> 0.05). In 691, two fertilization schedules (no fertilizer and fertilization with alfalfa pellets) and two fry stocking rates (250.000 and 375,000 fry/ha) were evaluated. Four ponds were used for each treatment. Statistically significant treatment differences were found in yield, number of fingerlings harvested/ha, average length, and average weight. Yield was higher in fertilized ponds compared with yield from unfertilized ponds at both stocking densities, but yield did not differ significantly between stocking density treatments given the same fertilizer treatment. Survival did not differ between density treatments, but total number of fish harvested was significantly greater from ponds stocked at the higher density. Fingerlings with the largest average weight were raised in fertilized ponds that were stocked at 250,00O/ha, while the smallest fingerlings were from unfertilized ponds that were stocked at 375,000ka. Days in culture interval, which varied among ponds by 9 days in 1990 and 10 days in 1991, was significantly correlated with most production variables in 1990 and with all production variables in 1991. Means of water quality variables were not significantly different between fertilized and unfertilized ponds in either year, but significant differences were found in means of three water quality variables between 1990 and 1991. Yield in both fertilized and unfertilized ponds in 1991 was less than in 1990.