The effects of hydrogen peroxide on the stress response of Atlantic Salmon (Salmo salar)

The effect of exposing Atlantic salmon Salmo salar to hydrogen peroxide was investigated to identify the acute and chronic effects of a single high dose on physiological measurements of stress. A total of 120 Atlantic salmon were divided into 3 groups, exposed to either saltwater (control), or 1000 and 1500 ppm H2O2, respectively, for 20 min. Treatment with H2O2 was found to be stressful to the healthy fish up to 24 h after exposure. Significantly increased cortisol and glucose concentrations were observed in fish treated with 1500 ppm, compared with the other two groups 6 and 12 h posttreatment. These levels returned to resting levels by 24 h. There were slight variations in mean plasma concentrations of sodium, chloride and potassium. The findings suggest that H2O2 may be used to treat Atlantic salmon for sea lice Lepeophtheirus salmonis, since it is relatively environmentally safe and breaks down easily in the water column. Although the use of 1500 ppm hydrogen peroxide, which has been cited to be acceptable for sea lice removal, presents short-term stress effects, physiological parameters normalize in 24 h. Changes in gill morphology are minor and not significant..