There’s lots of interest at the moment about how humans are impacting on the natural sounds of the oceans and seas. With increasing shipping and use of sonar and other sound based technology the background noise of the marine environment is changing.
A study just released indicates that a sound experiment conducted in 2006 lead to a significant fall in humpback whale song in the Stellwagen Bank National Marine Sanctuary (SBNMS) which was over 200 km away from the epxeriment site.
Fisheries management sonar impacts on humpback whales.
The Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiment was undertaken over 11 days during the autumn of 2006. The OAWRS is a mobile system that is used to monitor shoals of fish over a 100 km diameter. It operates using low frequencies pulses of sound. The system can be used in fisheries management and ecosystem monitoring.
The researchers compared the amount of humpback whales song in the marine sanctuary for 11 days before the experiment, the 11 days of the experiment and 11 days after the experiment. That 33 day period was then compared to the same 33 day period 2 years later in 2008.
Sound influenced whale song over 200 km away.
The study showed that there was a significant reduction in whale song during the period that the experiment was carried out. At 200 km this is the greatest distance of impact for man-made sound so far recorded on humpback whales.
While it is known that man-made sounds can impact on the songs of the humpbacks and other whales previous studies were concentrated on local effects of a few kilometres or so. This study has for the first time shown that sound can have impacts covering hundreds of kilometres.
Sound is an important communication tool for many whales. The humpbacks will sing during the mating season and will also sing on their long migrations. Previous studies have shown that whales will interact with surrounding noise. Whales have been known to change their songs in response to the sound of a motorboat for instance.
Other species of whales stop singing in presence of non-natural sounds.
Humpback whales are not the only species of whales to stop singing when anthropogenic noise is present. Sperm whales and blue whales have both been observed to stop singing in areas where seismic surveys are being carried out. Blainville’s beaked whales have also been observed to reduce their singing when ships using mid-frequency sonar are in the area.
External sites:
PLOSOne: Changes in Humpback Whale Song Occurrence in Response to an Acoustic Source 200 km Away
Incoming search terms:
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