Hydrogen peroxide treatments administered to hatchery-reared burbot: assessing treatment regimes from embrionic development through juvenile rearing

Burbot Lota lota is an emerging aquaculture species, in which fungal infestations during early life stage development are common. In this study, the tolerance of Burbot to external hydrogen peroxide (H₂O₂) treatment regimes was examined during four early life stages to determine species and life stage-specific sensitivity. Yolk-sac larvae tolerated three 1-h treatments up to 250 ìL/L H₂O₂ without significant reduction in survival. Preflexion larvae tolerated only 100 ìL/L H₂O₂ before survival was affected. In both cases, decreased survival was only observed after administration of three consecutive treatments. Flexion larvae tolerated up to 250 ìL/L H₂O₂, but by the juvenile stage sensitivity again increased to 100 ìL/L H₂O₂ before survival was affected. In these latter stages, decreased survival was observed immediately following the first H₂O₂ treatment, suggesting a mechanism for toxicity that is different than that in previous life stages. As has previously been shown, H₂O₂ can be effective for controlling aquatic bacteria and fungus at or below 250 ìL/L, and our results indicate that H₂O₂ concentrations currently used during Burbot egg incubation may be extended into the larval rearing stage for effective fungal control without negatively affecting survival of either eggs or newly hatched larvae. Additionally, treatment regimes may be continued through juvenile development for the purpose of controlling external pathogens in the hatchery production of Burbot.