Scottish Marine and Freshwater Science Vol 6 No 8
Little is known about effects of magnetic fields (MFs, 50 Hz, measured in Teslas) associated with high voltage cables on behaviour of European eels. It has previously been shown in a field study that swimming speed of European eels in the Baltic Sea slowed when crossing a 130 kV AC power cable. However, no details of fish behaviour during passage over the cable were recorded in this study, and it is not known whether the observed reduction in swimming speed was due to the MF associated with the cable, or some other factor. The aim of the present study was to observe the response of European eels at the silver eel stage of their life-cycle to an AC MF of approximately 9.6 µT at a fine scale in a controlled laboratory setting. During 28 trials, each lasting 4 hours and using a single eel per trial, 10 eels (termed “swimmers”) made between 1 and 43 passes through coils. There was no evidence of a difference in movement due to the MF nor observations of startle or other obvious behavioural changes associated with the magnetic fields. Level of movement decreased as the experiments progressed and increased with eel size. Eel passage through coils was unaffected by whether or not they were activated. In applying these results it must be kept in mind that the sample size was small, nocturnal behaviour was not tested and the field strengths were lower than might be encountered in the wild in some situations.
Data and Resources
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UK Open Government Licence (OGL)
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On the day of each trial, a single eel was introduced to the annular tank at approximately 09:00 hours. At approximately 11:30 hours, overhead red lights were switched on, overhead green lights were switched off, the video cameras were switched on and recording began. Each trial took place between 12:00 and 16:00 hours. This 4-hour trial period was broken down into two, 2-hour periods, each of which was an exposure period during which a MF was presented from either coils A and B or coils C and D as follows. At 12:00 hours, either coils A and B or coils C and D were switched on. At 14:00 hours, the energised coil set was changed i.e. if coils A and B were energised first, coils A and B were switched off and coils C and D were switched on, and vice versa. Brief visual checks for activity were made at approximately 13:00 and 15:00 hours. Each trial ended at 16:00 hours when either coils A and B or coils C and D were switched off as appropriate.
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Marine Scotland Science
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