Media Backgrounder: Seismic Blasting Threatens Marine Life

Batholiths Project

December 14, 2006
The project:
  • A team of academics, mostly Americans, want to study how the earth’s crust was formed.
  • They want to use a large airgun array (36 guns with a total volume of 6,600 in3) in the narrow fjords, inlets and coastal waters of the central coast of B.C.
  • The ship will tow the array at 4-5 knots and the airguns will be fired into the water every 20-60 seconds.
  • The academics hired a consulting company that prepared a draft Environmental Assessment report (EA) that states that there will be no significant environmental impact from the testing.
In response to the academics’ EA draft report:
  • Living Oceans Society contracted an independent review of the draft EA to assess the accuracy and quality of the document.
  • The reviewers, Dr. Robert McCauley and Dr. Chandra Salgado Kent, teach at the Centre for Marine Science and Technology at Curtin University in Australia and are recognized internationally for their expertise in seismic testing.
  • Although the draft EA states that there will be no significant environmental impact from the testing, Drs. McCauley and Kent found that this conclusion is not supported by science.
  • Their findings are available at www.livingoceans.org/library/index.shtml

How intense are the sounds from the airgun array?

In the immediate vicinity of the array, the sounds are reported to be 235 dB, These sounds can penetrate up to 50 km into the sea floor. The EA report predicts that whales and dolphins will be at risk of hearing damage if they are within 1,000-3,500 m of the array, as they would be exposed to 180 dB. (Note: dB = decibel, a unit used to measure the intensity of sound).

Why we are concerned

The proposed test area is biologically rich with a very complex bathymetry. Humpback whales and salmon will be migrating through the area during the proposed surveys. The inlets are rearing grounds for juvenile sablefish. The proposed track line of the survey passes near Rockfish Conservation Areas, exposing eggs and larvae to high-energy sound. Printable version of map available at www.livingoceans.org/media/index.shtml

One of the reasons for concern about seismic blasting is the inability to predict how sound will reverberate in the narrow parts of the channels and inlets. It is possible that whales, dolphins and porpoises may actually be herded further into the inlets as they attempt to flee the blasts which may expose them to even more intense sound levels.

What are the potential effects of seismic surveys on marine mammals?

Marine mammals living in the underwater darkness rely on sound to navigate, communicate, find and capture their prey and avoid predators. Scientists are just beginning to understand how increased noise affects mammals’ ability to carry out these functions, but we do know their responses to intense sounds include: habitat avoidance and/or abandonment, changes in vocal behaviour, longer dive times, shorter surface intervals with increased blow rates, masking of communication signals, aggression, pup/calf abandonment, annoyance, hearing loss (temporary and/or permanent) and tissue rupture.

What are the potential impacts of seismic surveys on fish?

Like marine mammals, fish rely on hearing for survival. As with marine mammals, many species of fish respond negatively towards high-energy sound such as the type that is produced from seismic surveys. Dr. McCauley conducted preliminary research where he exposed caged pink snapper to small (20 in3 ) airguns. After autopsy, all of the fish were found to have damaged hair cells and were effectively deaf. McCauley’s preliminary study is a wake up call that shows the need for more careful systematic research about the impacts of seismic surveys on marine life.

 

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