May 26 2011

EM Effects – Elasmobranchii

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For elasmobranchii, the aspect of electromagnetic fields is very important as they are extremely sensitive to them (Gill 2005).  They are so sensitive and reliant on these fields that they deserve special consideration when evaluating the impacts of anthropogenic EM fields on the environment.  They use EM fields to detect prey at both long and short distances, as well as to navigate (Fields 2007).  Sharks in particular are extremely sensitive to the signals emitted by struggling fish (Ohman 2007).  This differs from the use of EM fields by other fish in that the scope of usage expands well beyond navigation and into daily life function.  Skates, as bottom dwellers, would be physically closest to the lines and thus susceptible to sensory confusion.  In some cases, magnets are used as a repellent to keep sharks away from commercial fishing nets (Robbins 2011).  While these magnets are specialized for this purpose, it is entirely possible the fields from the transmission lines could have the same effect.  Whether the EM fields from transmission lines serve as attractant or repellent to sharks in nature has yet to be studied.

This image illustrates how a shark receives the EM signals emitted by its prey.

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