Increased Walleye Egg Hatch and Larval Survival after Protease Treatment of Eggs

Abstract

Abstract Various techniques for eliminating the clumping of newly spawned walleye eggs (Stizostedion vitreum) were evaluated by measuring hatch, growth, and survival. Percent hatch was highest (83%) in egg groups water hardened in 0.01% protease solution. Other water-hardening techniques tested were: (1) continuous stirring; (2) 250 mg/L tannic acid solution; and (3) bentonite clay suspension. Low hatching percentages for eggs continuously stirred or treated with bentonite were attributed to fungus. Fungus was minimal on eggs treated with protease or tannic acid. Fish hatched from each egg treatment group were intensively cultured for 21 d in one of four rearing environments: (1) well water; (2) well water receiving 1% sea salt for the initial 3 d; (3) well water receiving a 6-mL daily addition of antifoam emulsion for the initial 9 d; or (4) well water receiving both the 1% sea salt and antifoam treatments. There was slightly higher survival in larval fish hatched from eggs treated with protease or tannic acid and reared in well water containing 1% sea salt. We observed no differences in average fish length among the test groups.