Name: Milton S. Love
Offshore renewable energy facilities transmit electricity to shore through submarine power cables. Electromagnetic field emissions (EMFs) are generated from the transmission of electricity through these cables, such as the AC inter-array (between unit) and AC export (to shore) cables often used in offshore energy production. The EMF has both an electric component and a magnetic component. While sheathing can block the direct electric field, the magnetic field is not blocked. A concern raised by fishermen on the Pacific Coast of North America is that commercially important Dungeness crab (Metacarcinus magister Dana, 1852)) might not cross over an energized submarine power cable to enter a baited crab trap, thus potentially reducing their catch. The presence of operating energized cables off southern California and in Puget Sound (cables that are comparable to those within the arrays of existing offshore wind energy devices) allowed us to conduct experiments on how energized power cables might affect the harvesting of both M. magister and another commercially important crab species, Cancer productus Randall, 1839. In this study we tested the questions: 1) Is the catchability of crabs reduced if these animals must traverse an energized power cable to enter a trap and 2) if crabs preferentially do not cross an energized cable, is it the cable structure or the EMF emitted from that cable that deters crabs from crossing? In field experiments off southern California and in Puget Sound, crabs were given a choice of walking over an energized power cable to a baited trap or walking directly away from that cable to a second baited trap. Based on our research we found no evidence that the EMF emitted by energized submarine power cables influenced the catchability of these two species of commercially important crabs. In addition, there was no difference in the crabs’ responses to lightly buried versus unburied cables. We did observe that, regardless of the position of the cable, Cancer productus in southern California tended to move to the west and Metacarcinus magister tended to move to the east.
U.S. Bureau of Ocean Energy Management [contract number M14AC00027]
California and Washington, United States
- To investigate whether fish movement behaviors were affected by the energization of the cable,
- Whether the energization of the cable hindered or facilitated outward migration of LFC smolts
Overall, our experiment shows that both rock and Dungeness crabs are neither more likely nor less likely to cross a power cable to enter a baited trap. This lack of a discriminating response to the presence of a power cable at the entrance of a baited trap was consistent between rock and Dungeness crabs regardless of whether the crabs were observed to move into the traps on the day of the deployment or had moved into the traps sometime unknown between the times the divers left the site and returned the next day.
Love, M.; Nishimoto, M.; Clark, S.; McCrea, M.; Bull, A. (2017). Assessing potential impacts of energized submarine power cables on crab harvests. Continental Shelf Research, 151, 23-29.