Evidence suggests cetaceans utilise magnetoreception to navigate using magnetic fields. However, disturbances in the geomagnetic field from solar storms and anthropogenic activity can lead to beachings. Previous studies indicate fluctuations around 50 nT are large enough to influence strandings. Ísafjarðardjúp is home to a large humpback whale population in the summer, but marine activity, including fish farms, vessel traffic and coastal structures such as the Bolafjall radar station, makes the fjord prone to magnetic interference, potentially intefering with magnetoreception.
To study the extent of disruption in the marine environment, a marine magnetic survey was conducted using a proton-spin magnetometer to map magnetically unstable regions of the fjord, which coincided with frequent whale sightings. This would highlight areas of the fjord where interference with magnetoreception is likely to occur, potentially leaving cetaceans vulnerable to disorientation, which could lead to navigational errors and beaching.
Areas of instability that were prone to magnetic disturbances were located in the middle of the fjord near Vigur Island and at the entrance. Instability in these regions show a 0.58 point-biserial correlation coefficient for creating fluctuations of 10 to 50nT within a 7km radius of the fish farms, and creating regions of 'extreme instability' with fluctuations above 50 nT located within 5 km of the farms. Bolafjall radar station situated near the entrance of the fjord is hypothesised to be responsible for extreme disturbances fluctuating as high as 230 nT.
Approximately 20% of cetacean sighting hotspots overlap with these unstable regions, and instability at the entrance of the fjord can potentially cause disorientation to cetaceans attempting to enter and exit. Therefore, policies, such as shielding submarine cables and restricted use of radar in vulnerable areas, are suggested in this study to reduce the risk of cetacean strandings.
