Various technologies have been developed for fish guidance at hydropower and water diversion projects. Historic attempts to guide fish with electricity used alternating current (AC) for deterrence. This paper highlights an approach to fish guidance that combines new developments in the use of electric fields to direct or block fish movements. These include the ability to: (1) vary and control pulsed DC waveforms; (2) remotely monitor and adjust output levels; (3) implement safeguards to minimize potential human or animal interactions with deterrence fields; and (4) create Graduated Field Fish Barriers (GFFBs) for various fish guidance needs in fisheries management, invasive species and hydropower-related applications. We review the efficiencies of GFFBs and other bottom-mounted electric guidance arrays (which can be up to 100% effective) from results in peer-reviewed literature as well as non-published reports. Published accounts primarily address deployments to block movements of invasive species (e.g. Asian carp in the Chicago Sanitary and Ship Canal). There are 47 GFFB electric arrays in use around the world for fish guidance and deterrence. However, hydropower facilities using GFFBs are limited to three deployments to date (a tailrace barrier for a power plant in Vessy, Switzerland, a tailrace barrier at Beeston hydropower facility in the U.K., and a downstream penstock application in British Columbia, Canada). This paper highlights “the lessons learned” in applying electric barrier technology and addresses its successes, challenges, limitations and design modifications to enhance effectiveness. Whereas guidance and deterrence barriers have been largely successful for upstream-moving species, only limited success has been achieved with downstream-moving fish. Accordingly, we discuss a new but untested concept for guiding downstream-moving fish: a downstream-angled array of electrodes (either surface-suspended or bottom-mounted) that could be used in combination with other deterrence technologies to induce movement away from intake structures before fish become incapacitated by the electric field.
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