Cardiovascular changes and catecholamine release following anaesthesia in Chinook salmon ( Oncorhynchus tshawytscha) and snapper ( Pagrus auratus)

We investigated recovery from anaesthesia in Chinook salmon ( Oncorhynchus tshawytscha) with and without surgery. Fish either underwent light sedation on exposure to 60 ppm AQUI-S™ or surgical depth anaesthesia with 120 ppm AQUI-S. Surgical depth anaesthesia experiments were replicated using New Zealand snapper ( Pagrus auratus). During light sedation, there was no evidence of catecholamine release in salmon despite changes in heart rate and blood pressure. Following surgical anaesthesia both salmon and snapper released high concentrations of catecholamines into the circulation. Plasma half-life of adrenaline in salmon was 9.3±0.7 min ( n=7) and in snapper was 4.4±3.3 min ( n=7). There was no further release of catecholamines, despite attempts by both species to escape their enclosures. Though clearance of the catecholamines was rapid, the cardiovascular effects of anaesthesia were prolonged. Dorsal aortic blood pressure ( P DA) and heart rate (HR) were high following anaesthesia, falling by 60 min in the 60 ppm exposed salmon but remaining high in the 120 ppm group. Following anaesthesia ventral aorta blood pressure ( P VA) in snapper was positively correlated with HR, as was P DA and haematocrit in salmon. Recovery of cardiovascular control processes is prolonged in recovery from anaesthesia if the fish become hypoxic.