Causes of High Mortality among Cultured Larval Walleyes

After 40 years of research in North America, the problem of variable and low survival of young walleyes Stizostedion vitreum during rearing remains unresolved. In laboratory experiments, a period of high mortality was identified when postlarvae shifted from endogenous to exogenous feeding. The main factors that influenced mortality were food density, the timing of food availability, fish density, and culture volume. Larvae at different developmental stages showed different responses to these factors. Cannibalism within a cohort caused significant mortality during the postlarval stage. An optimum food density of 100 daphnids per liter, a larval density of less than 1 fish per liter, a minimum culture volume of 20 liters, and immediate food availability when larvae first feed are suggested to increase survival of postlarvae.