Whales disturbed by seismic surveys

Seismic surveys used for oil and gas prospecting on the sea floor are a disturbance for blue whales, biologists have confirmed.

Lucia Di Iorio of Zurich University, Switzerland and Christopher Clark, an acoustics specialist at the Cornell Laboratory of Ornithology in New York, recorded the calls of blue whales at a feeding ground in Canada's St. Lawrence estuary. The 11-day experiment was conducted during a period when a survey vessel was using a "sparker", a low-to-medium power device that sends an acoustic pulse to the sea floor and picks up the reflected signal to get a picture of the topography. The days the vessel was operating, the whales called more than two and a half times more frequently than on days when the vessel was not operating.

Further research work is now needed to show whether blue whales actually suffer stress or other problems relating to the noise. One concern is that oil and gas prospecting is venturing out into ever-deeper water, and little is known about the impact this might have on whales' feeding and migratory patterns. They are solitary animals and therefore their feeding areas are very important because they have the chance to get together in a small range and with a lot of social activity as well.

The study, published in Biology Letters, provides the first evidence that blue whales change their calling behaviour when exposed to sounds from seismic surveys and suggests careful reconsideration of the potential behavioural impacts of even low source level seismic survey sounds on large whales.