how these organisms detect magnetic fields is still unknown, it is generally believed that they are able to detect magnetic cues, such as the Earth’s geomagnetic field, to orientate during migration. With reference to the East Anglia THREE project the relevant groups are teleosts (bony fishes, i.e. salmon and eels), crustaceans (lobsters, crabs, prawns and shrimps) and molluscs (snails, bivalves and cephalopods).
229. The sensitivity of the main receptors found in the local study area for which there is evidence of a response to E or B fields, together with an assessment of the potential impacts arising from the proposed worst case cabling, is given below separated for elasmobranchs, diadromous migratory species and other fish species.
Elasmobranchs 230. Elasmobranchs are the species group that are considered to be the most electro- sensitive. These species naturally detect bioelectric emissions from prey, conspecifics and potential predators and competitors (Gill et al. 2005). They are also known to detect magnetic fields. Laboratory and field experiments using AC cables of the type used by the offshore renewable energy industry, showed that EMF emitted was within the range of detection by electro sensitive species such as rays and dogfish. It was not possible to determine whether the EMF emitted from the power cables had a direct impact on the species used (Gill and Taylor 2001; Gill et al. 2005; Gill et al 2009; CMACS 2003; COWRIE 2009).
231. For AC cables rated between 33kV and 132kV iE fields which could cause avoidance in elasmobranchs are not expected. Such iE fields are only expected to occur within 1m or less from the cable surface of 220kV and 275 kV HVAC cables. Burial would reduce this small avoidance zone either completely should burial be to a depth of 1m (effectively negating avoidance), or to tens of centimetres should burial be to a depth of 0.5m.
232. Similarly, for HVDC cabling, iE at which avoidance in elasmobranchs could occur are only expected within a few tens of centimetres (bundled) or 1m (separated) of 320kV cables. Avoidance behaviour would be expected at only slightly greater distances from 500 kV cables (0.5m if bundled and 1 - 2m if separated). Again, burial would reduce these small avoidance zones completely for bundled cables even at 0.5m burial depth and at 0.5m and 0.5 - 1.5m if separated for 320 kV and 500kV HVDC cables respectively. For 600 kV cables the distances would be expected to be only slightly further than those presented above for 320 and 500 kV cables.
233.
It has been speculated that elasmobranchs may be confused by anthropogenic E field sources that lie within similar ranges to natural bioelectric fields. Laboratory behavioural studies have demonstrated both AC and DC artificial electric fields
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 11 Fish and Shellfish Page 76
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