Tank Performance of Larval Saugeyes (Walleye × Sauger) Produced Out‐of‐Season and during Regular Season Spawning

Abstract

AbstractIn the north‐central region of the United States, hybrid saugeyes (female walleye Sander vitreus [formerly Stizostedion vitreum] × male sauger S. canadense) have been recognized as an important species for recreational fisheries and as a potential aquaculture commodity. We compared the performance of larval saugeyes that were produced out of season with larvae produced during the regular spawning season using intensive rearing systems. Fertilized out‐of‐season and regular season saugeye eggs that were produced by crossing two Spirit Lake, Iowa, female walleyes and two Mississippi River male saugers were obtained from the Rathbun Hatchery, Iowa Department of Natural Resources, Moravia. Out‐of‐season spawning was induced by light and photoperiod manipulation. Eyed eggs were air‐shipped overnight at 10°C. First‐feeding larvae (19,000 fish/tank) were stocked in six 800‐L cylindrical tanks provided with turbid water to prevent cannibalism and with surface sprays to secure swim bladder inflation. The fish were fed exclusively with commercial diets (Fry Feed Kyowa B‐400 and B‐700 and Bio‐Oregon starter diet). The specific growth rate (SGR), condition factor, and survival were compared between saugeyes reared out of season (50 d) and during the regular season (39 d). The mean SGR and survival of saugeyes from the out‐of‐season experiment were significantly lower than those of saugeyes from the regular season experiment (P < 0.05), although the condition factor of the fish did not differ between the experiments. Significant differences in SGR were also observed between tank replicates, suggesting possible differences in the feeding responses of saugeyes within a tank system. Large discrepancies (40–43%) were observed between actual survival at the end of the rearing period and predicted survival based on counts of dead larvae siphoned from the tank bottom, suggesting the occurrence of cannibalism and the deterioration of larvae bodies prior to tank cleaning. The actual survival (12–19%) of larval saugeyes in both experiments shows some promise in the intensive rearing of saugeyes exclusively on dry feeds.