A new report from the Bureau of Ocean Energy Management (BOEM) addresses four questions about the impact of submerged power cables on fish and invertebrates, the principal one being whether electromagnetic fields (EMF) from submerged power cables attract or repulse fish or invertebrates.
The purpose of the study was to shed light on the potential effects of energized, seabed deployed, power cables on marine organisms, broadly applicable to planned and future renewable energy projects in the Pacific Outer Continental Shelf (OCS) region and other OCS planning areas.
The experimental design tested for the effect of inshore versus deep water cable placement. Researchers found that few biological effects could be detected from patterns of species relative abundance, and there was no evidence of behavioral response by electro-sensitive species. These findings may help inform appropriate mitigation measures for the permitting of undersea power cables.
BOEM’s Pacific Region office and research partners from the University of California Santa Barbara undertook this experiment in a natural setting using existing, undersea power cables connected from three drilling platforms in the Southern California OCS–Platforms Heritage, Harmony and Hondo, at depths to about 326 meters (1069 feet)–to Las Flores on the mainland. The cables run from the platforms toward the mainland to a sea floor depth of 10 meters (about 33 feet), and from there are buried inshore. All of these cables use the industry standards of the power cables that will be used for connecting devices (35 kilovolts) within renewable energy installations.
During the three-year study, researchers conducted 38 days of fish surveys, 30 days of invertebrate studies and 38 days of plant studies–in February for the nearshore areas and October for the offshore areas. Over all habitats, they observed 4,671 individuals of a minimum of 44 species of fishes. They also observed a total of 30,523 invertebrates from at least 43 invertebrate species.
According t BOEM, four key findings stand out:
1) Researchers did not observe any significant differences in the fish communities living around energized and unenergized cables and natural habitats;
2) They found no compelling evidence that the EMF produced by the energized power cables in this study were either attracting or repelling fish or macro invertebrates;
3) EMF strength dissipated relatively quickly with distance from the cable and approached background levels at about one meter from the cable and;
4) Cable burial would not appear necessary strictly for biological reasons.