Assessment of Formalin and Hydrogen Peroxide Use during Egg Incubation of North American Burbot

Abstract

Control of aquatic fungi in the family Saprolegniacea during egg incubation was investigated as part of a program aimed at developing aquaculture methods for Kootenai River burbot Lota lota maculosa, a species relatively unknown to North American aquaculture. The concentration effectiveness of two antifungal control methods, formalin and hydrogen peroxide, was compared over two consecutive breeding seasons in a newly developed micro-incubation system. The results indicated that daily 15-min treatments of 1,667 mg of formalin/L and 500 mg of hydrogen peroxide/L inhibited fungal growth on eggs and increased egg survival by up to 200% during the incubation period relative to the untreated controls. Lower concentrations of 1,000 mg/L formalin and 250 mg/L hydrogen peroxide also yielded increased survival but were not sufficient to completely inhibit fungal growth on eggs. Concentrations up to 5,000 mg/L formalin and 500 mg/L hydrogen peroxide did not appear to negatively influence egg survival during any stage of development. Gross larval deformities observed 7 d after the first observed hatch were not significantly different between any antifungal treatment group and the untreated controls. Thus, to maximize egg survival and adequately control fungus during egg incubation for this species, a minimum of 1,667 mg/L formalin or 500 mg/L hydrogen peroxide is recommended.