A sonar device used for offshore oil and gas exploration has been implicated in the stranding of approximately 100 melon-headed whales (Peponocephala electra) in 2008 in a lagoon in Madagascar. The high death toll was also a result of the remoteness of the area where the strandings occurred.
The remote location affected the amount of time it took to find the animals and mount a response to attempt to move the animals out of the lagoon. It also increased the difficulty in getting survivors to open water.
On 30 May, 2008, the pod of whales was found in the Loza Lagoon in northwest Madagascar. At least 75 animals died, despite efforts by the Wildlife Conservation Society and the International Fund for Animal Welfare to herd the animals to the open ocean. Most deaths were attributed to emaciation, dehydration, sun exposure and other secondary effects of the animals being out of their normal habitat.
The Independent Stranding Review Panel, facilitated by the International Whaling Commission, found that
“Multi-Beam Echosounder System (MBES) use to be the most plausible and likely behavioral trigger for the animals initially entering the lagoon system.”
This is the first time this particular device has been connected with a mass stranding of cetaceans. Other types of anthropogenic (human created) sound, including military sonar, have been cited in strandings of beaked whales, harbour porpoise, orca, and other species of whale and dolphin.
The independent review was conducted in conjunction with the US Marine Mammal Commission, the US National Oceanic and Atmospheric Administration, the US Bureau of Ocean Energy Management, ExxonMobil Exploration and Production (Northern Madagascar) Ltd, the International Fund for Animal Welfare, the Wildlife Conservation Society and the Government of Madagascar.
While some reports focus on Exxon Mobil’s role in the incident, it is important to be aware that all companies involved in oil and gas exploration use various types of seismic arrays, as do various military and research vessels. Efforts to monitor presence of marine mammals in areas where exploration is occurring offer a chance for preventing such incidents.
According to Dr. Howard Rosenbaum, Director of the Ocean Giants Program for WCS. “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. ”
Sources:
Southall, B.L., Rowles, T., Gulland, F., Baird, R. W.,and Jepson, P.D. 2013. Final report of the Independent Scientific Review Panel investigatingpotential contributing factors to a 2008 mass stranding of melon
headed whales (Peponocephala electra) in Antsohihy, Madagascar. Accessed online 30 September 2013.
Whale mass stranding attributed to sonar mapping for first time. Accessed online 30 September 2013.
Exxon Mobil's hunt for oil killed 100 melon headed whales. Accessed online 30 September 2013