Physiological response of spotted knifejaw (Oplegnathus punctatus) during transportation in offshore aquaculture net pen

Abstract

Fish transportation is an important process during offshore fish farming. Plasma cortisol, glucose, hepatic and muscular glycogen, hematological parameters (white blood cell [WBC], red blood cell [RBC], hemoglobin [Hb] hematocrit [Hct]), hepatic anti-oxidant (superoxide dismutase [SOD], catalase [CAT], and glutathione peroxidase [GSH-Px]), aspartate-aminotransferase (AST) and alanine-aminotransferase (ALT) activities, malondialdehyde (MDA) content, histological alteration, apoptosis and stress-related gene expression (mr, gr1, gr2, hsp70, hsp90a, hsp90b) of spotted knifejaw were investigated during land sea relay transportation to identify the main stressor and illustrate the underlying physiological response. Results showed that handling and transport stress significantly increased plasma cortisol and glucose contents, whereas hepatic glycogen decreased and muscular glycogen remained unchanged throughout the transport. WBC and RBC number, Hb and Hct contents, ALT and AST activities, MDA levels, and hepatic SOD, CAT, GSH-Px activities exhibited similar trends to cortisol under handling and transport stress. Meanwhile, handling and transport stress induced hepatocyte vacuolization, nuclear migration, and hepatocytes apoptosis. Hepatic mr, gr1, gr2, hsp70 and hsp90a mRNA levels were significantly up-regulated under handling and transport stress. Handling stress accounted for 64.29% of the alternation of the above parameters throughout transport process. The aforementioned parameters recovered to normal levels after transportation for 72 h. These results indicated handling, not ship-transport stress was the main stressor of spotted knifejaw during land sea relay transportation, while stress-induced negative effects were alleviated after 72 h.