Marine seismic surveys are a major disturbance for blue whales

29/09/2009 09:22:45 Seismic surveys disrupting Blue whales
September 2009. Blue whales are forced to ‘shout' to be heard when swimming near seismic surveys, new research from Canada's Gulf of St Lawrence reveals. 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 experiment was conducted while a survey vessel was using a low-to-medium power acoustic device that sends an acoustic pulse to the sea floor to create a picture of the topography.

Whales called much more frequently
"When the survey vessel was operating, the whales called more than two and a half times more frequently than on days when the vessel was not operating," said Di Iorio.

Further research is required to find out what affect the seismic surveys may have on the whale's social habits. Blue whales are usually solitary, but gather at feeding grounds and also communicate across vast distances with their own voices.

Further concern
Another concern is that oil and gas prospecting is venturing out into deeper water, and little is known about the impact this might have on whales' feeding and migratory patterns. In April, an experiment reported in the same journal found that very loud, repeated blasts of sonar caused an Atlantic bottlenose dolphin to temporarily lose its hearing. Numerous beachings of whales, dolphins and porpoises have occurred over the past decade, and several have coincided with naval exercises, indicating that the blame may lie with the sonar used during warship exercises.

Blue whales
It is thought that there are between 5,000 - 12,000 Blue whales alive today. They can grow as long as 100 feet and weigh as much as an extraordinary 180 tonnes. Blue whales were hunted to the verge of extinction before they was given international protection in 1966.

The results were published in the specialist journal " Biology Letters"