Humpback Whales in Madagascar, photo by Marco Zanferrari on Flickr

Fleets of seafaring vessels have used sonar mapping to gain a clear picture of the ocean for years – however recently there has been growing concern over the effects of sonar on sea mammals. Now, for the very first time, an independent study confirms that this technique is responsible for a large-scale marine mammal stranding. In 2008, 100 melon-headed whales from the Loza Lagoon system in northwest Madagascar washed ashore due to sonar activities conducted by ExxonMobil Exploration and Production Limited.

whale stranding, madagascar, melon headed whale, sonar mapping

After the 2008 stranding, a team led by the International Fund for Animal Welfare and Wildlife Conservation Society released the remaining live whales back into the open sea and performed necropsies on the dead animals. Their findings concluded that the 75 whales who expired died from the impacts of high-frequency sonar mapping.

“Implications go well beyond the hydrocarbon industry, as these sonar systems are widely used aboard military and research vessels for generating more precise bathymetry (underwater mapping). We now hope that these results will be used by industry, regulatory authorities, and others to minimize risks and to better protect marine life, especially marine mammal species that are particularly sensitive to increasing ocean noise from human activities. ” said Dr. Howard Rosenbaum, Director of the Ocean Giants Program for WCS.

The report concluded that a multi-beam echosounder system operated by Exxon’s survey boat was the main cause of the stranding. Exxon, who partially funded the panel, rejected their assessment and denied responsibility. The report could have major consequences for the US Navy who have been criticized for injuring whales and dolphins with their sonar mapping and testing. The hydrocarbon industry may also be forced to review their use of seismic air guns when exploring for oil and natural gas on the ocean floor.

+ Wildlife Conservation Society

Via ScienceDaily

Images via NOAA and IFAW