Assessment of potential impact of magnetic fields from a subsea high-voltage DC power cable on migrating green sturgeon, Acipenser medirostris

Empirical evidence suggests that marine animals perceive and orient to local distortions in the earth's natural magnetic field. Magnetic fields (MFs) generated by electrified underwater cables may produce similar local distortions in the earth's main field. Concern exists that these distortions may impact migration movements of MF-sensitive animals. The Trans Bay Cable (TBC) is a +/- 200-kV, 400-megawatt, 85-km high-voltage direct current transmission line buried through San Francisco Bay (37(degrees )56' 8.81 N, 122(degrees) 27' 0.19 W). Detections of adult green sturgeon implanted with acoustic transmitters were used from six cross-bay receiver arrays from 2006 to 2015 to investigate how inbound and outbound migration movements through lower portions of their route to/from upstream breeding grounds are related to the TBC's energization status (off/on) and other local environmental variables. Here, we assess how these variables impacted transit success, misdirection from the migration route, transit times, and migration path locations within stretches between the Bay's mouth and the start of the Sacramento River. Overall, there was varied evidence for any effect on migration behavior associated with cable status (off/on). A higher percentage of inbound fish successfully transited after the cable was energized, but this effect was nonsignificant in models including temperature. Outbound fish took longer to transit after cable energization. Inbound and outbound migration path locations were not significantly influenced by cable energization, but results suggest a potential subtle relationship between energization and both inbound and outbound paths. Overall, additional migration-based studies are needed to investigate the impact of anthropogenic cables on marine species.

Automated summary

Empirical evidence suggests that the distortions in the earth's magnetic field caused by underwater cables may impact the migration behavior of marine animals. This study examines the effects of the Trans Bay Cable (TBC) on the migration movements of adult green sturgeon. The results show that the energization of the cable is associated with a higher success rate of inbound migration, but a longer transit time for outbound migration. The cable energization does not significantly affect the migration path locations, but there may be a subtle relationship. Further migration-based studies are needed to investigate the impact of anthropogenic cables on marine species.