For decades, monitoring marine mammals via bioacoustics has relied on hydrophones: underwater microphones designed to record and convert sound waves into electrical signals. Hydrophones have shaped much of what we know about cetaceans today, from identifying dialects, tracking migration, measuring noise pollution, and even estimating population presence without disturbance. But hydrophones are fixed and only listen where they’re dopped. If whales pass outside their detection range, we can’t hear them and gain critical data. Expanding coverage often means deploying more hydrophones which involves more cost, more maintenance, and more infrastructure.
Hydrophone stationed at Gray’s Reef National Marine Sanctuary, courtesy of NOAA
Researchers from the University of Washington Bothell’s School of STEM and School of Oceanography, with funding from Allen Family Philanthropies have found a way to advance bioacoustics with already-existing infrastructure.
Across the world’s oceans lie millions of kilometers of fiber optic telecommunication cables. Most installed to carry internet and data between continents. However, many have gone underused, dormant, or simply functioning as expected, but with no ecological role.
In the Puget Sound, Dr. Shima Abadi, an oceanographer and professor at UW Bothell’s School of STEM and a joint appointment at UW’s School of Oceanography, with her research team are changing that. Using a technology known as Distributed Acoustic Sensing (DAS), fiber optic cables can be transformed into continuous acoustic arrays.
The cable being brought to shore to be connected to the interrogator by Dr. Shima Abadi and her research team.
“The fiber optic cables connect to an instrument known as an interrogator, which sends laser pulses through the cable and measures when it is affected by vibrations or acoustic energy. This allows researchers to pinpoint and analyze the precise location and nature of the disturbance. “
The distinction between hydrophones and DAS is significant, especially for studying species such as the Southern Resident killer whales. In a region shaped by vessel traffic, warming waters, and declining salmon availability, understanding not only if whales are present but where they are moving in real time across thousands of kilometers could meaningfully inform management and conservation outcomes.
Orcas in the presence of a whale-watching vessel, courtesy of Wolfgang Lucht
If successfully implemented at scale, this approach could meaningfully strengthen how we monitor and respond to endangered marine mammal populations. Earlier and broader detection of whales who spend most of their time out of sight could support stricter vessel management, improve our understanding on how movement patterns shift in response to prey availability or warming waters, and over time could reveal trends that single-point monitoring might miss.
Over the next two years, Dr. Abadi, her team, and local non-profit organizations will collect data and compare to previous hydrophone insights, in hopes of learning how to mitigate negative impacts on orcas and other wildlife.
Credit
Using light to hear the whales, The University of Washington, Bothell
Thumbnail: Matriline of Northern Resident killer whales, courtesy of NOAA Fisheries, Vancouver Aquarium