Sonar exposure on marine mammals

By Dr. Frans-Peter Lam (TNO)

Over the last decade, several strandings of cetaceans coincident with military sonar exercises have raised great concern over the effects of sonar exposure on marine mammals. Still, many aspects of cause-effect and potentially critical levels of exposure remain unknown.
TNO has been conducting research investigating the effect of sonar signals on marine mammals since 2006. The project - called 3S - is executed in close cooperation with the Sea Mammal Research Unit (SMRU), the Norwegian Defence Research Establishment (FFI) and Woods Hole Oceanographic Institution (WHOI). Since 2009, Leiden University has been involved as an external partner. The 3S project is funded by the Office of Naval Research, the Royal Netherlands Navy, the Royal Norwegian Navy, Norwegian Ministry of Defense and WWF Norway.
The research is conducted in the form of sea-going trials, whereby whale and dolphin groups are tracked for several hours, before, during and after exposure to military sonar sounds. Four 3S research trials have been conducted off Norway, investigating the effects of sonar exposure on killer whales, pilot whales and sperm whales. Data is collected by means of suction cup tags (recording dive characteristics and acoustics), visual observations of the behavior of whale and dolphin groups at the surface and by towed hydrophone arrays. TNO plays a leading role in the observations of whale and dolphin group behavior, in the recording and analysis of acoustic parameters by a specialized hydrophone array (Delphinus; able to locate the position of the animals) and contributes the sonar source (Socrates).
The research collective has made use of one of the special features of the area off northern Norway: the 24h daylight. The suction-cup tags which are placed on the animals can remain attached for 15 hours, or longer. The tagged animal is followed throughout that time by visual observers who make use of the 'polar day' to keep tracking the animals. From 2011 onwards the research will travel even more north, to the waters off Svalbard, looking for new species and aiming to help in the establishment of safe use of military sonar worldwide.
Willem Barentsz Poolinstituut

Bundeling van kennis, onderzoek en onderwijs over de Noord- en de Zuidpool






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