Transport‐induced changes in hypothalamic–pituitary–interrenal axis gene expression and oxidative stress responses in Coilia nasus

Netting, loading and transporting can induce stress in fish, often resulting in death and subsequent economic losses to the aquaculture industry. Coilia nasus is strongly responsive to stressors, thus this species presents a suitable model for research of the stress response. In this study, we investigated whether hypothalamus–pituitary–interrenal axis genes were involved in stress responses to transport in C. nasus. mRNA expression profiles of corticotropin-releasing hormone (CRH), urotensin I (UI) and pro-opiomelanocortin (POMC) in the brain and glucocorticoid receptor (GCR) in the head kidney were assessed by quantitative reverse transcription polymerase chain reaction (PCR) analysis. The results revealed a significant decrease in CRH and UI expression levels in the brain of stressed C. nasus, while POMC expression was significantly increased. In contrast to those three genes, GCR expression levels were significantly lower at 2, 4 and 6 h and significantly greater at 8 h after transport. To investigate whether oxidative stress was induced by transport, we assessed expression levels of oxidative stress biomarkers. Levels of lipid peroxides and malondialdehyde in liver were profoundly increased after transport, while liver glutathione peroxidase activities were significantly increased. Superoxide dismutase and catalase activities were significantly reduced, as compared with those in control fish, suggesting that oxidative stress may be induced by transport in C. nasus. Currently, there is little information regarding physical stressors, such as transport, loading, and netting and induction of oxidative stress in fish, which may be an important mechanism by which transport stress causes death.