Comparative Performance of Intensively Cultured Larval Walleye in Clear, Turbid, and Colored Water

Abstract

Abstract The purposes of this study were to verify the findings of a previous study that showed improved performance of walleyes Stizostedion vitreum raised in turbid water (16.1–49.7 nephelometric turbidity units, NTU), to determine the minimum level of turbidity that would reduce or eliminate the tendency of fry to cling to tank sidewalls, and to evaluate a dye (Aquashade) as a substitute for increasing turbidity with clay. Fish were reared from 2 to 21 d posthatch in clear water (0.3 NTU), turbid water (23.8 NTU), and water colored blue with Aquashade at 1.8 and 17.4 mg/L. Fish in turbid water began consuming feed earlier than those in clear water or in either of the dye solutions. At the termination of the experiment, survival, gas bladder inflation, length, and weight were significantly greater for fry reared in the turbid water than in the other three treatments. In turbid water, survival was 35.1 %, with 99.3% gas bladder inflation. The mean weight of fry reared in turbid water was 270–380% greater than the mean weight of fry from the other treatments. Measurements of cannibalism indicated no cannibalism in turbid water tanks and 1.1–1.7% cannibalism in the other treatments. The tendency of fry to cling to the sidewalls of the tank was reduced substantially at 5 NTU and eliminated at 23 NTU. The study demonstrates that culture of walleye fry in a facility supplied with clear water (i.e., turbidity < 5 NTU) will be substantially enhanced by an artificial increase in turbidity.