skip to main content


Title: Chinook salmon and green sturgeon migrate through San Francisco Estuary despite large distortions in the local magnetic field produced by bridges

Empirical evidence exists that some marine animals perceive and orient to local distortions in the earth's main static geomagnetic field. The magnetic fields produced by undersea electric power cables that carry electricity from hydrokinetic energy sources to shore-based power stations may produce similar local distortions in the earth's main field. Concerns exist that animals migrating along the continental shelves might orient to the magnetic field from the cables, and move either inshore or offshore away from their normal path. We studied the effect of the Trans Bay Cable (TBC), an 85-km long, high voltage, direct current (DC) transmission line leading underwater from Pittsburg, CA to San Francisco, CA, on fishes migrating through the San Francisco Estuary. These included Chinook salmon smolts (Oncorhynchus tshawytscha) that migrate downstream through the San Francisco Estuary to the Pacific Ocean and adult green sturgeon (Acipenser medirostris), which migrate upstream from the ocean through the estuary to their spawning habitat in the upper Sacramento River and return to the ocean after spawning occurs. And based on a detailed gradiometer survey, we found that the distortions in the earth's main field produced by bridges across the estuary were much greater than those from the Trans Bay Cable.more » The former anomalies exceeded the latter by an order of magnitude or more. Significant numbers of tagged Chinook salmon smolts migrated past bridges, which produced strong magnetic anomalies, to the Golden Gate Bridge, where they were recorded by dual arrays of acoustic tag-detecting monitors moored in lines across the mouth of the bay. Additionally, adult green sturgeon successfully swam upstream and downstream through the estuary on the way to and from their spawning grounds. Hence, the large anomalies produced by the bridges do not appear to present a strong barrier to the natural seasonal movement patterns of salmonid smolts and adult green sturgeon.« less
ORCiD logo [1] ;  [1] ;  [2] ;  [3]
  1. Univ. of California, Davis, CA (United States). Dept. of Fish, Wildlife and Conservation Biology
  2. Electric Power Research Inst. (EPRI), Palo Alto, CA (United States)
  3. Virginia Commonwealth Univ., Richmond, VA (United States)
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
Additional Journal Information:
Journal Volume: 12; Journal Issue: 6; Journal ID: ISSN 1932-6203
Public Library of Science
Research Org:
Electric Power Research Institute, Inc., Palo Alto, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1374975