The survival and respiration response of two abalones under short-term hypoxia challenges

Anthropogenically increased occurrence of hypoxic conditions in the aquatic environment, combined with climate change-induced temperature increase, is causing increased concern for aquaculture species. In this study, the survival of the Pacific abalone Haliotis discus hannai (DD) and its hybrid offspring (H. discus hannai female x H. fulgens male, DF) were observed under 96 h hypoxia at both optimum temperature (20 degrees C) and high temperature (28 degrees C). The respiration rates (MO2) of DD and DF facing acute hypoxia at three temperatures (20 degrees C, 25 degrees C, and 28 degrees C) and progressive hypoxia at three different sizes (2 cm, 4 cm, and 6 cm) were compared. At 20 degrees C, there was no significant (p > .05) difference between median lethal concentrations (LC50) of DD and DF while considering all time intervals; however, at 28 degrees C, 96 h DO LC50 of DF (3.18 mg/L) was lower than that of DD (4.82 mg/L), indicating that DF displayed stronger hypoxia tolerance ability than DD at 28 degrees C. MO2 of DD and DF increased with rising temperature and larger sizes under acute and progressive hypoxia tests, while DF showed higher MO2 than DD, indicating its better plasticity of oxygen uptake. These results suggest that DD might be more vulnerable to a combination of thermal and hypoxia stress than DF, revealing that hybridization could be a useful way to improve stress-resistance for the abalone aquaculture industry.