Innovative Non-Lethal Electric Fields for Marine Mammal Deterrence: Results of Trials on Seals and Sea Lions

Pinniped populations have increased exponentially since passage of the Marine Mammal Protection Act.  These population increases have resulted in elevated levels of predation on ESA-listed fishes in the Pacific Northwest, complicating recovery efforts for fishery managers.  Growing numbers of marine mammals also damage docks in mooring basins, posing challenges for harbormasters.  This presentation describes a novel concept to control marine mammal predation on fishes using non-lethal, electric gradients to deter pinnipeds in rivers and their presence in harbors where animal/human use conflicts occur.  Our paper focuses on the support trials conducted on captive animals to assess the feasibility of developing the technology for pinniped deterrence in the wild (however, a version of the technology is being used currently for deterrence of wild harbor seals in the Fraser River, B.C.).  The electric deterrence technology can be combined with hydroacoustics for passive operation (cued only when sonar identifies marine mammals at specific sites), and with light or sound stimuli to help condition avoidance behaviors.  The technology delivers brief pulses of direct current without injury to pinnipeds or nearby fish.  The low-voltage, DC gradient does not affect boats or boat traffic.  A brief video will highlight the extreme sensitivities documented during trials on harbor seals (British Columbia) and California sea lions (Moss Bay Marine Labs), with and without food present.  Although spring Chinook salmon hesitated when approaching a deterrence field in an extreme, worst-case trial (continuous, non-stop operation), extensive tests on other fish species show that steelhead, Pacific lamprey and sturgeon are not deterred at the sea lion deterrence level.  Results suggest that selective deterrence of marine mammals is possible (especially during intermittent operation of the array) — an opportunity to help fishery co-managers and harbormasters resolve controversial resource conflicts with marine mammals.