The Consequences of Pulsed DC Electrofishing and Air Exposure on Rainbow Trout

Abstract

Electrofishing, which is widely used for fish collection, is a procedure that is often followed by handling and air exposure before the fish are released. Although the consequences of electrofishing are not fully known, some studies suggest that physical damage such as skeletal injury and mortality can result. Physiological disturbances resulting from stimulation of the stress axis and impaired ventilation have also been reported following electroshock. In the present study, rainbow trout treated with pulsed DC electroshock, in fact, showed no evidence of direct mortality, and skeletal damage was only induced under the most severe conditions. Physiological disturbances in the absence of physical damage consisted of a lactacidosis and stimulation of the stress response. The lactacidosis was likely induced by tetany during immobilization and impaired ventilation during immobilization and early recovery. These disturbances, which persisted for at least 4h, were greater than those reported following DC electrofishing. They were, in fact, similar in magnitude and duration to 2-3 min bout of exhaustive exercise. Swim performance following pulsed DC electroshock was also impaired for at least 1 h. If fish were air exposed immediately following pulsed DC electroshock the stress response and lactacidosis tended to be more severe and swim performance was further impaired.