May 25 2011

EM Effects – Fish

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The electric and magnetic fields emitted by generators and transmission lines at sea will likely have some effect on fish.  The main source of these fields will be the transmission lines rather than the actual wind or wave harvester (Gill 2005).  Although the cables are coated so as not to emit electric fields, magnetic fields are still emitted and these in turn induce new electric fields outside the line’s insulation.  Studies show that the fields will only be substantial in relatively close proximity to the lines.  This standard levels of field emitted lies within the known detectable range for numerous species of fish.  Many fish use electromagnetism to navigate or locate other fish, so the forecasted results would either be attraction to or repulsion from the lines, depending on the fish type.

Migrating species of fish partially rely on magnetism to orient themselves and studies indicate that the fields from transmission lines could disrupt the patterns to which they are accustomed (Ohman 2007).  Yellowfin tuna, a popular seafood choice, has been proven to be one such type of fish.  One study showed that nets with magnets attached to them had a 50% higher catch rate than the controls (Tanski 2004).  Magnetic fields of greater strength than natural ones proved to attract both adult and juvenile fish.  This is a strong indicator that the magnetic fields emitted by the wires may serve to attract fish during their migration patterns.  With fish such as Yellowfin tuna being magnetically sensitive, this could have commercial fishing implications.  OREDs could serve as either recreational fishing grounds or protected fishing areas if they prove to cause fish congregation in large numbers as studies indicate is possible.  This cannot be assumed for all fish types however, as a study on eels showed no migratory disturbance in the presence of a windmill (Ohman 2007).

The effects of magnetic fields may extend to the physiological realm as well (Ohman 2007).  Certain species of fish showed increased hormone production or hindered embryo development when in the presence of a sustained magnetic field.  These studies were done in captivity, and the possible implications for the wild cannot readily be assumed.  Unfortunately, few studies specifically catered to ocean transmission lines currently exist.

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