Toxicity of Hydrogen Peroxide to Pre‐exposed Young‐of‐the‐Year Walleye: Effects of Water Hardness and Age of Fish

Abstract

Abstract.— Young‐of‐the‐year (Age 0+) walleyes Stizostedion vitreum were exposed to hydrogen peroxide at 10 mg/L for 1 h in an effort to increase their tolerance to subsequent exposures to hydrogen peroxide at therapeutic concentrations that are considered to be toxic. The effects of age of fish and water hardness on the effectiveness of this pre‐treatment protocol were examined. Trials were performed in fish at four ages (50‐d, 60‐d, 86‐d, and 95‐d post‐hatch) and under three different water quality conditions (soft water: hardness = 64.4 mg/L, alkalinity = 56.5 mg/L; medium hard water: hardness = 103.3 mg/L, alkalinity = 51.5 mg/ L; hard water: hardness = 130.3 mg/L, alkalinity = 92 mg/L). A benefit of pre‐treatment was only observed when it was performed under hard water conditions and only with walleyes at 60‐ and 86‐d post hatch. The pre‐treatment protocol appeared to be detrimental to fish in the youngest age group (50‐d post‐hatch) under all three water quality conditions.