Whales and sonar

The preservation and wellbeing of the whale populations that migrate and congregate around Australia’s coastline is of considerable public interest. Its importance is emphasised by the fact that whale populations migrate annually through key Defence offshore exercise areas on the east and west coasts.

The potential effect of active sonar on marine mammals has attracted significant media attention in recent years. While the scientific evidence is still inconclusive, there is sufficient circumstantial evidence of a possible linkage between the use of some mid-frequency active sonars and the stranding of beaked whales in northern hemisphere waters.

Precautionary approaches adopted by the Royal Australian Navy (RAN) aim to reduce the exposure of marine mammals to high levels of acoustic energy that might affect their health or interfere with behavioural characteristics.

The use of active sonar by the Navy remains an important operational requirement that provides warships with the ability to detect potentially hostile submarines. A combination of active and passive sonar systems is needed to detect increasingly quiet conventional submarines in likely operational areas for the RAN. It is important to note that the use of active sonar by Navy vessels is infrequent. Sonar is usually only used during occasional exercises with submarines, or switched on briefly for a daily functionality check. Sonars are inactive at most times when RAN ships are at sea.

Environmental impact assessments, strict mitigation measures and being reactive to scientific research are just some of the tools that Navy employs to minimise its impact on marine mammals. The mitigation measures determine that if marine mammals are detected in close proximity to a Navy ship during an activity that might involve emission of high levels of underwater sound, either from sonar or underwater explosions, the ship or personnel concerned will relocate or delay the activity.