Before any offshore oil drilling takes place, oil companies perform exploratory tests, or seismic survey, in order to make sure that hydrocarbons are present in the area. The "Old Harry" deposit, where seismic surveys have been authorized by the Canada-Newfoundland and Labrador Offshore Petroleum Board, is located in the middle of the Gulf of St. Lawrence's Laurentian channel. The channel is a fish-pass for numerous marine species, including the blue whale (Balaenoptera musculus) whose Atlantic population is very low (and appears on the species at risk public registry), and the Atlantic cod (Gadus morhua) whose status in the Gulf of Saint-Lawrence remains worrisome.
To conduct a seismic survey, compressed air streams or focused sonic waves are sent towards the ocean floor in order to gauge the depth, location and structure of the valuable geological resources that lie underneath.
Since sound travels more easily under water than through the air, the noise from a single seismic survey can travel tens of thousands of square kilometres. A DFO report and an article in the Canadian Journal of Zoology show that seismic surveys increase noise levels to twice (20 dB) the normal level, and impact marine life. Indeed, more and more scientists confirm that such surveys disturb the communication, navigation and eating habits essential to the survival of marine wildlife. These sonic waves can also damage fish with air bladders, destroy marine wildlife eggs and larvae, and incite fish and other marine species to temporarily migrate away from the affected area.
This kind of oil and gas prospecting inevitably causes environmental damage to a marine environment. The Quebec government confirmed how risky hydrocarbon prospecting and development is for the biodiversity of the St. Lawrence estuary in their Strategic Environmental Survey (SEA).
Since the estuary and the gulf are inextricably linked, it's easy to assume that tourism and commercial fishing within the gulf would also be affected by seismic surveys.