Accounting for Water Temperature during Hydrogen Peroxide Treatment of Channel Catfish Eggs

—The effect of water temperature on the efficacy of hydrogen peroxide (H2O2) as a disinfectant for channel catfish Ictalurus punctatus eggs was examined at 248C and 288C. Eggs at each temperature were treated with H2O2 at 0, 100, 250, 500, or 1,000 mg/L as a daily 15-min bath. Mean hatching success at 248C was greatest (P . 0.05) for eggs treated with 250 and 500 mg/L H2O2, hatching success tending to increase with increasing treatment concentration between 100 and 500 mg/L. The opposite effect was observed at 288C: hatching success was greatest (P , 0.05) for eggs treated with 100 and 250 mg/L H2O2,, hatching success tending to decrease with increasing H2O2 concentration between 100 and 500 mg/L. The results of this research, together with previously published results, demonstrate that there is a negative correlation between H2O2 concentration and water temperature with respect to the optimal efficiency of H2O2 as an egg disinfectant and suggest that there is an increased toxicity of H2O2 at higher temperatures. Careful consideration of temperature is necessary when disinfecting channel catfish eggs with H2O2. Hydrogen peroxide (H2O2) was initially reported by Marking et al. (1994) to be effective for controlling fungal (Saprolegnia sp.) infections of fish eggs; it has since been investigated as an alternative treatment to control fungal infections of eggs of several additional fish species (Waterstrat and Marking 1995; Schreier et al. 1996; Rach et al. 1998; Arndt et al. 2001; Barnes et al. 2003). Currently, H2O2 is designated by the U.S. Food and Drug Administration (FDA) as an aquaculture drug of low regulatory priority (LRP) when administered at concentrations as great as 500 mg/ L. Small and Wolters (2003) investigated the effectiveness of H2O2 as a treatment for disinfecting channel catfish Ictalurus punctatus eggs, considering hatching success and embryo survival in various H2O2 treatment regimes ranging in concentration from 0 to 500 mg/L at a water temperature of 268C. They found a once-daily 15-min bath in H2O2 at 250 mg/L significantly improved hatching success and yielded the greatest embryo survival. * Corresponding author: [email protected] Received September 29, 2003; accepted December 12, 2003 In contrast, Rach et al. (1998) reported using treatment regimes at concentrations as great as 3,000 mg/L to improve channel catfish hatching success at a water temperature of 228C. The effect of temperature on H2O2 efficacy as a chemotherapeutic for aquaculture was first demonstrated when treating gill ectoparasites that affected coldwater fishes (Bruno and Raynard 1994; Kiemer and Black 1997; Treasurer and Grant 1997). Those studies, which showed increased mortality associated with H2O2 treatment at increasing temperatures, led to management recommendations to reduce treatment times at higher temperatures. Toxicity of H2O2 also appears to increase with temperature for warmand coolwater species at postlarval life stages (Rach et al. 1997); however, little information exists regarding the effect of temperature on eggs and embryo survival during H2O2 treatment. Differences in reported optimal H2O2 concentrations for treating channel catfish eggs at 228C (1,000 mg/L; Rach et al. 1998) and 268C (250 mg/L; Small and Wolters 2003) suggest temperature-related toxicity trends are similar whether treating postlarval fish or eggs. In the present study, channel catfish eggs incubated at 248C and 288C were treated with increasing concentrations of H2O2 to determine what concentration yielded the greatest hatching success. These findings on the effect of temperature are discussed with consideration of the results observed by Rach et al. (1998) and Small and Wolters (2003).