A study published in the journal Aquatic Mammals described what it called the most thorough, robust and practical approach to minimizing and monitoring the risk of harm to vulnerable marine species when intense sounds are used in seismic surveys of the sea floor, primarily in the search for oil and gas, the International Union for the Conservation of Nature reported.
In seismic surveys, air guns towed behind ships repeat powerful bursts of sound, with sensors recording the return echo to reveal details of the sea floor and underlying geologic structure to a depth of several miles.
Whales rely on sound for communication, navigation and foraging, so exposure to loud noise in such surveys can result in stress and behavior changes, affect foraging and nursing or cause direct physical damage.
The study -- conducted by Sakhalin Energy Investment Company Ltd., with Gazprom, Shell, Mitsui and Mitsubishi as shareholders -- describes the most comprehensive whale protection program ever developed for a seismic survey, in a survey close to the main Western Gray Whale feeding area near Sakhalin Island, on the Russian coast, just north of Japan.
"The survey was completed on schedule and all monitoring and mitigation components were successfully implemented. The company obtained the necessary data, while, at the same time, minimizing the risk of disturbance to whales," said Carl Gustaf Lundin, IUCN director of the Global Marine and Polar Program.
"Key to minimizing impacts during seismic surveys is advance knowledge of marine life distribution and migrations and timing a survey accordingly," said study co-author Greg Donovan, an expert with IUCN's Western Gray Whale Advisory Panel. "In the Sakhalin case that means conducting the survey as early as possible in spring when the ice has melted but most of the whales have not yet arrived."
The mitigation techniques in the Sakhalin survey -- including real-time visual and acoustic monitoring of noise levels, whale locations and behavior, before during and after the survey -- could be adapted to seismic surveys in any environmentally sensitive area, the study authors said.
"We hope our guidelines on how to reduce the environmental impacts of seismic work in the oceans will find their way into the manuals of energy companies and environmental agencies around the world," Doug Norwacek of Duke University said.
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