Two new studies on seismic survey impacts have been released by the Joint Industry Program (JIP) Sound and Marine Life research program, funded by oil and gas companies.

The first looked at the effectiveness of “soft start” ramp up of seismic survey airguns at night and at times of poor visibility.  This has become standard procedure, but there have been some concerns that if marine mammals were very close to the ship, even the low sound levels at the start of the ramp up could be loud enough to cause hearing damage.  Based on two different modeling approaches, the study found “no instances…in which the threshold levels for hearing injury for cetaceans were reached during the initial stages of the soft-start sequence. This suggests that the animals are not at significantly greater risk of harm when a soft start is initiated in low visibility conditions.”  Link to pdf of report at the website of the International Association of OIl and Gas Producers.

The second study aimed to address “the rarely-charted relationship between oil Exploration and Production (E&P) activities and trends in cetacean stocks.”  The study cites case studies involving populations of sperm whales in the Gulf of Mexico, humpback whales, blue whales and fin whales off the coast of California, northern bottlenose whales off Nova Scotia and harbour porpoises and minke whales off the east coast of the UK. The study, published in Aquatic Mammals,  provided new insights into the worldwide distribution of E&P activity in relation to marine mammal populations and has also revealed striking data gaps in our understanding of cetacean population numbers and trends. While the report’s review of seven stocks “found signs of an increase in numbers in one population (Californian humpback whales),” for the remaining six, “population trends could not be assessed due to the high variability in the abundance estimates.”  Link to pdf of this report.

In essence, there is not enough data to really tell us whether ongoing oil and gas activity has reduced stocks over the long term.  As usual in the many cases where ocean noise and population studies come up against this paucity of solid data, the researchers recommend that someone should fund of future studies ‘that provide more comprehensive data on cetacean stocks.”

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