HOUSTON – Powerful acoustic devices used by oil companies searching for new sources of hydrocarbons in the Gulf of Mexico have had no discernible effect on endangered sperm whales living in those waters, according to a federally funded study released Thursday.
The six-year, $9.3 million study examined the impact of offshore seismic activity, which involves firing air guns into the water, on the Gulf's sperm whale population, estimated to be around 1,600.
Most of the whales live in the northern Gulf, often in areas heavy with exploration and production operations.
“The two are not mutually exclusive,” said Randall Luthi, director of the U.S. Minerals Management Service, which oversees E&P activities in federal waters and which funded the study. “That's the kind of knowledge we need to have.”
Fifteen federal and state agencies, universities and other organizations collaborated on the study which sought to establish baseline information about the whales' biology and behavior.
It also sought to determine the effect of man-made noise like seismic probes for subsea oil and natural gas. Powerful air guns are fired from specially equipped boats, though federal guidelines restrict crews from using the acoustic equipment if they spot a whale within one-third of a mile from the vessel.
The technology is used to determine the geologic makeup of the seabed.
“The bottom line is that air-gun noise from seismic surveys that are thousands of yards distant does not drive away sperm whales living in the Gulf,” said Doug Biggs, a professor of oceanography at Texas A&M University and a study participant.
However, Biggs said some whales, when diving deep into the Gulf to eat, reduced the rate at which they searched for prey when scientists carried out controlled seismic experiments. Biggs and others acknowledged the whales have been exposed to such noise for several decades, so it's impossible to say how they behaved before the oil companies arrived.
The study involved a sample of 98 tagged sperm whales, the species Herman Melville wrote of in “Moby-Dick.” An adult male can measure 50 feet long and weigh up to 50 tons. It can remain underwater for more than hour before surfacing for air.
To the surprise of marine biologists nearly a decade ago, a significant number of sperm whales were found making a permanent home in the Gulf of Mexico near the busy mouth of the Mississippi River. Their emergence within a few miles of the Louisiana coast was considered remarkable because sperm whales rarely hunt close to shore. Whales often hunt at depths of 3,000 feet or more.
The MMS study found some genetic and social differences among the Gulf sperm whales and those in the North Atlantic and the North and Mediterranean seas. It also found the whales to be smaller than those in other regions.
“The study has greatly contributed to our knowledge of sperm whales ... (but) it's also raised new questions we need to know more about, such as their feeding and breeding patterns,” Biggs said. “There's still a lot we don't know about these huge creatures.”
Concerns about the impact of offshore exploration on whales and other marine species is not limited to the Gulf of Mexico.
In May, Alaska Native and environmental groups sued to stop exploration by oil companies in Arctic waters frequented by whales, seals and other marine species. The groups are challenging federal permits that allow the companies to search for oil and gas using acoustic devices.
The plaintiffs claim the signals could disrupt tens of thousands of animals as they feed, socialize and travel through the seas of northern Alaska. They say it's especially worrisome to Alaska Natives in the region who depend on the marine mammals for food and worry they will desert traditional hunting areas for quieter waters.
The Minerals Management Service and National Marine Fisheries Service, both of which grant permits, are defendants in
the suit.
