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

—Action 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. Predation of California sea lions Zalophus californianus on returning adult Pacific salmon Oncorhynchus spp. along the West Coast of North America, particularly in the Columbia River basin, has become an increasing concern for biologists and fishery managers striving to conserve and restore threatened and endangered salmonid populations. Indeed, in November 2008, the National Marine Fisheries Service issued a Letter of Authorization allowing the Oregon Department of Fish and Wildlife, Washington Department of Fish and Wildlife, and Idaho Department of Fish and Game to lethally remove California sea lions deemed a threat to endangered salmonids (U.S. Department of Commerce 2008; U.S. District Court for the District of Columbia 2008). A potential alternate means to prevent the upstream movements of California sea lions is through the use of low electric fields conducted through a modified electrical fish barrier system (Bonneville Power Administration 2007), hereafter referred to as an electrical sea lion barrier system. An electrical sea lion barrier system creates an electrical field within the water column to deter California sea lion movement upstream. The system is designed to operate at electrical power levels far below guidelines established by state and federal agencies for electrofishing of salmonid fishes (NMFS 2000; WSDOT 2006), and the system uses a pulsed direct current (DC) frequency lower than 15–30 Hz, which is intended to minimize injury to nontargeted fish (Reynolds 1996; Reynolds and Holliman 2004). Nevertheless, given that electrical fields have been applied in North America since the 1950s to alter and Subject editor: Tim Essington, University of Washington, Seattle * Corresponding author: [email protected] Received July 27, 2009; accepted September 23, 2009 Published online December 21, 2009 363 Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science 1:363–377, 2009 Copyright by the American Fisheries Society 2009 DOI: 10.1577/C09-039.1 [Article]