Acoustic study helps document changing Arctic

Indigenous hunters, fishermen helped to deploy recorders off St. Lawrence Island

Acoustic monitoring of whales, walrus and seals in the northern Bering Sea is helping scientists learn more about these marine mammals under drastic pressure from climate change.

The four-year study released by the Wildlife Conservation Society on Feb. 3, a collaborative effort with Columbia University, Southall Environmental Associates and the University of Washington, was published in the journal Marine Mammal Science. The project, also publicized by EurekAlert, the online publication of the American Association for the Advancement of Science, notes that this was the first study to conduct year-round acoustic monitoring for marine mammals off St. Lawrence Island in the Bering Sea. The goal was to determine how seasons, sea surface temperature and sea ice influence the presence, distribution and movements of five species of endemic Arctic marine mammals.

According to Emily Chou of the Wildlife Conservation Society and lead author of the study, data gathered will serve as an important baseline for future monitoring of effects of climate change, subsequent sea ice changes and expected increases in shipping on distribution of the region’s marine mammals. The study between 2012 and 2016 focused on bowhead and beluga whales, walrus, bearded seals and ribbon seals.

With the help of local indigenous hunters and fishermen, the scientists deployed archival acoustic recorders in three northern Bering Sea locations.

“Working with local residents to deploy and retrieve equipment was an important part of our effort to keep the work as locally-based as possible,” said co-author Martin Robards.

Acoustic monitoring is the most effective way of determining seasonal presence of these species in these challenging Arctic areas, given unpredictable weather conditions variable daylight and variable ice conditions, said another co-author Brandon Southall. It also can be used to measure variability in ocean noise from both natural and human sources, such as shipping and how they may affect behavior and well-being of marine mammals, he said.

Altogether the recorders logged over 33,000 individual vocalizations from whales, walruses and seals. The study supported previous scientific and traditional knowledge about distribution of marine mammals in that area, with a finer-scale resolution than previously available.

Scientists said they hope this work and continued monitoring at strategic locations in this area will help identify trends caused by long-term changes in environmental conditions and human-related activities.

Study funds were provided by the North Pacific Research Board in Anchorage, the Flora Family Foundation and the U.S. National Science Foundation’s Office of Polar Programs.