Behavioral and Physiological Response of White Sturgeon to an Electrical Sea Lion Barrier System

Abstract

AbstractAction agencies have encouraged the development of a modified electrical fish barrier system to deter upstream movements of California sea lions Zalophus californianus as a means to reduce their predation on returning adult Pacific salmon Oncorhynchus spp. within rivers along the West Coast of North America. Given that the barrier system does not discriminate which species will experience electrical shock, we studied the potential effects of the sea lion barrier on the survival, behavior, physiology, and injury of white sturgeon Acipenser transmontanus. Fish subjected to acute electroshock had high survival (100%). Conversely, fish that became entrained within the electric field and therefore experienced chronic electroshock had lower survival (93%). White sturgeon altered their behavior by spending significantly more time avoiding the area over the barrier when electrical power was applied as compared with controls. Fish that experienced acute electroshock spent more time remaining motionless, presumably recovering from physiological disturbance. Our results indicate that white sturgeon had significantly higher plasma lactate than controls and that lactate remained at elevated levels for at least 4 h after electroshock. Plasma glucose, ion concentrations (chloride, sodium, and potassium), and indicators of cell damage (plasma hemoglobin and enzyme activity of aspartate transaminase) did not differ between electroshocked fish and controls. We did not observe any notable hemorrhages or notochord injuries in white sturgeon that experienced electrical shock. Our results suggest that the location for the electrical barrier system should be rigorously examined before barrier deployment and that the dates, frequency, and duration of use should be further refined to ensure that negative effects on nontarget species such as white sturgeon are minimized.