East Anglia ONE
EMF Assessment
(Lamna nasus), angel (Squatina squatina) and basking (Cetorhinus maximus) sharks, and skates (Dipturus spp.). A number of spawning grounds are known to occur off East Anglia (Coull et al 1998; Ellis et al 2012) including herring, cod, plaice, sand eels and sole (as well as the invertebrate, Nephrops norvegicus or Norway lobster), with associated nursery grounds, as well as thornback ray and tope nurseries.
With respect to the EAONE project, only 275kV HVAC and HVDC cabling are likely to generate B fields above background levels, and even worst-case scenarios (separated deployment of higher rated designs) result in attenuation below these levels over distances of approximately ten meters, with bundled deployment resulting in propagation to just a few meters. Pelagic species, such as herring, mackerel, salmon, porbeagle and basking sharks are therefore likely to be unaffected, unless venturing into very shallow waters. Benthic fish species are more likely to encounter the B fields, and are possibly even still able to detect them at distances at which they fall below the geomagnetic field (Westerberg 2000; Meyer et al 2004; see Section 4.3). However, it is thought that any effects upon teleost or elasmobranch orientation behaviour are likely to be small and temporary (akin to demonstrations of eel deviation; Westerberg 2000; Ohman et al 2007), with normal movement/migration expected to resume once beyond the few to ten distances mentioned above, or slightly further should fields below background levels still be detectable.
In areas where rock dumping or mattresses are used (at cable crossings or areas of hard substrate) there is potential for smaller species to encounter strong magnetic fields of up to approximately 5000µT or more in the case of separated deployment. An example would be small-spotted catsharks, the females of which segregate from aggressive males by sheltering in rocky crevices (Sims et al 2001). Whether any physiological effects on such rock-dwelling fish could result from these stronger fields is uncertain. The only evidence relates to fish embryonic development, which has been shown to be delayed by AC B fields of 1 to 100µT (Cameron et al 1985; Cameron et al 1993). Shallow sandy areas, in particular, are important nursery areas for many fish species (e.g. thornback rays, flatfish, sand eels), but in areas of such substratum, the cables are likely to be buried which would prevent fish (including eggs and juveniles) from encountering the stronger fields.
6.1.3. Marine mammals and chelonians
Marine mammals are strongly linked with the use of geo-navigation by detection of variation in magnetic fields (e.g. Kirschvink et al 1986, who correlated strandings with local magnetic minima). However, the ability has not been demonstrated experimentally, and how the sense operates remains unconfirmed. There is no evidence of cetacean migration being affected by sub-sea cable B fields. Harbour porpoise (Phocoena phocoena) migration across the Skagerrak and western Baltic Sea has been observed unhindered despite several crossings over operating sub- sea HVDC cables (Walker 2001). Eight species of marine mammals occur regularly in the North Sea; namely harbour and grey seals, harbour porpoises (the most numerous; estimated at 268,000 in 1994), bottlenose, white-beaked and Atlantic white-sided dolphins, and killer and minke whales (SMRU 2001). Most are markedly more common further north, off Scotland. A further fifteen cetaceans and five
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