Offshore oil and gas development threatens the
coast long before the
first drop of oil or gas is extracted from the seabed. The first step
in development is seismic testing to provide information about where oil is most
likely located. Seismic testing is done
with an array of 15 to 45 air guns that send explosive shock waves
every 10 to 25 seconds into the seabed that then echo back through the
water. The sound is loud enough to disrupt, injure or possibly lead to
the death of fish and marine mammals. Surveys can last several
months.The sounds emitted from seismic air guns travel far in the ocean environment. For example, seismic testing that took place off the coast of Cape Breton was recorded in the Bahamas. According to Dr. Chris Clarke, Director of the Bioacoustics Research Program at Cornell University, seismic testing is the modern form of exploratory dynamite. He says that , “air guns represent the most severe acoustic insult to the marine environment that [he] can imagine, short of naval warfare.”
Read Dr. Clarke’s submission to the hearings on seismic
testing in Cape Breton.
Seismic testing occurs throughout the entire time
the offshore oil and gas industry operates in a particular
area.
Marine mammals living in the underwater darkness rely on sound to
navigate, communicate, find and capture their prey and avoid predators.
Increased noise affects their ability to survive. There is evidence that high-intensity
sound from sonar and air guns leads to strandings and subsequent
death of beaked whales.
The critically endangered Sakhalin gray whale population in the western North Pacific has been found to react to seismic surveys at distances greater than 30 km. High levels of seismic surveys in that region seem to have displaced the whales from their critical habitat. The whales will avoid an area where seismic testing is occurring, even if it is in critical feeding grounds.
Read
more about the impacts of seismic testing on the Sakhalin
gray whale population.
High pressure sound can also harm fish. The deafening noise causes some fish swim bladders to explode, such as rockfish. The high energy sound waves kill marine larvae and disrupt the traditional migratory paths of some fish as well as whales and dolphins. In some places, these disturbances have resulted in reductions in commercial fish catches of up to 50 percent, and have caused whales to leave waters where they are habitually found.
A
Norwegian study found that seismic
testing affects fish distributions for 18 to 20 nautical miles (33
to 37 km) around the shooting area, and resulted in trawl
catch decreases of 70 percent in the shooting area and 50 percent
over the entire study area. This decrease in catch rates lasted
for at least five days (the experiment ended before all catch
rates recovered).
A recent DFO study on the impact of seismic testing on the snow crab found crabs had damaged ovaries and internal organs, and some lost their legs. Changes were also observed in crab behaviour
