The use of underwater power cables is expanding globally due to increased interest in offshore energy production and energy transportation through marine environments.  However, there is concern that the electromagnetic fields (EMF) induced by current passing through these cables may alter the behavior and physiology of marine species, with potentially lasting effects on migration, feeding habits, reproductive potential, and population or community status.  Despite this concern, few studies have investigated these effects in free-living species.  In 2009, a 85 km long high-voltage DC (HVDC) power cable was placed within the San Francisco Bay, running parallel, then perpendicular to, the migration route of anadromous species moving between the ocean and the inland river systems.  In this study, we assess the impacts of this HVDC cable on the migration behaviors of EMF-sensitive fish genera.  Specifically, we examined juvenile salmonids (Chinook salmon, Oncorhynchus tshawytscha, and steelhead trout, Oncorhynchus mykiss) during their outward migration to the ocean, and adult green sturgeon, Acipenser medirostris, during their migration from the ocean to their riverine spawning grounds and back again.  Fish movements were monitored using acoustic telemetry and passive tracking techniques involving uniquely-coded ultrasonic transmitters in fish and arrays of tag-detecting hydrophone receivers throughout the Bay.  The magnetic field produced by the HVDC cable was measured using a transverse gradiometer and mapped at the major locations of telemetry arrays within the bay.  A model of the cable's magnetic field was developed which closely matched the empirically measured values and can be used to calculate the strength of cable's magnetic field at different distances from the source.  Results will show a comparison of fish migration behaviors (e.g., percent of successful migrations, duration of migration, time spent near vs. far from cable, etc.) before and after the cable was activated.