Sub-optimal or reduction in temperature and salinity decrease antioxidant activity and cellularity in the hemolymph of the Pacific abalone (Haliotis discus hannai)

This study investigated the oxidative stress and hemocyte responses of Pacific abalone exposed to various water temperatures (4, 6, 8, and 10 °C) and salinities (26, 30, and 34 psu) for 7 days, to identify their tolerance ranges of temperature and salinity. The survival rate of Pacific abalone ranged from 98.7 to 100% at 8 °C and 10 °C, but dropped to 25–55% at 4 °C at all levels of salinity. The levels of superoxide dismutase and glutathione in the hemolymph were significantly higher at 4 °C and 6 °C than in the controls in all salinity groups, indicating that these temperatures induced greater stress in the Pacific abalone. Total hemocyte count was lowest at 6 °C in the 26 psu group. The percentages of apoptotic and necrotic cells were higher in the 26 psu group than in the other salinity groups, and higher in the 4 °C and 6 °C groups than in the other temperature groups. These results indicate that the lowest tolerance to water temperature and salinity in the Pacific abalone was 8 °C and 30 psu, respectively. •Survival rate of Pacific abalone decreased sharply at 6 °C and 26 psu.•Low water temperature and salinity caused oxidative stress in Pacific abalone.•Temperature and salinity had a combined effect on the physiology of Pacific abalone.•Lowest tolerance of abalone for temperature and salinity was 8 °C and 30 psu.•These results can be used as reference data to reduce abalone mortality in culture.