The effect of hydrogen peroxide concentration and water temperature on yellowtail kingfish Seriola lalandi in a repeated bathing treatment

Abstract

Hydrogen peroxide is routinely used in commercial yellowtail kingfish culture to treat monogenean infections. As the culture of this species expands into warmer geographical areas, this study aimed to compare the effects of a repeated exposure to different hydrogen peroxide concentrations at two rearing temperatures, 18 and 26 °C. The repeat bath occurred 14 days after the initial bath in line with commercial treatment regimes. The three concentrations tested were 85, 170 and 340 mg L−1, with bathing conducted for 30 min. Mortality occurred following the second bath at 340 mg L−1 at 26 °C.The highest hydrogen peroxide dose caused epithelial lifting in gill filaments and significantly reduced the size and abundance of common mucus cells within the skin epithelium following the repeat bath in warm water. Despite the highest dose causing gill damage and mortality in warm water, there were no significant effects of hydrogen peroxide concentration on any of the conventional blood parameters, except in moribund fish. A novel measurement of plasma thiol oxidation, however, was found to be significantly elevated at the highest bathing concentration.Whilst yellowtail kingfish appeared to be tolerant of the high concentration of hydrogen peroxide tested in the current study at ambient water temperature, these fish were not infected with monogeneans, and any such burden is likely to increase the susceptibility of the fish to the effects of hydrogen peroxide.