Researchers Lower 1.3-Mile Fiber-Optic Line to 'Hear' Endangered Orcas — Could Subsea Internet Cables Become Whale Microphones?

University of Washington team tests fiber-optic lines as undersea listening devices

Researchers from the University of Washington recently lowered 1.3 miles (about 2.1 km) of fiber-optic cable into waters off Washington state to test whether the same thin glass lines that carry internet traffic can also record vocalizations from endangered southern resident orcas.

Using fiber-optic sensing techniques — such as Distributed Acoustic Sensing (DAS) that turn a single cable into a continuous array of acoustic sensors — the team hopes to convert these slender fibers into reliable, around-the-clock listening devices. If successful, the thousands of miles of fiber-optic cable already laid across the seafloor worldwide could be repurposed as a large-scale system for monitoring marine life.

Why it matters: Fewer than 75 southern resident orcas remain in the Salish Sea, where they face threats from vessel noise, contaminated water and declining prey. Chinook salmon, the orcas’ primary food source, have declined by more than 60% since 1984 because of habitat loss, overfishing, dams and warming waters.

The fiber-optic system functions like one long sensor and can map an animal’s approximate location and travel routes with high resolution. Earlier tests near Oregon detected the low, deep calls of fin and blue whales, but orcas use higher-frequency clicks and whistles that have not yet been proven detectable with this approach.

If the method works for orcas, it could provide practical conservation tools: real-time alerts for ferry operators and vessel traffic (for example, warning Washington State Ferries when whales approach Seattle so ships can slow or delay noisy operations), and continuous data to study orca behavior. Recordings might reveal how orcas alter calls during hunts, how they coordinate to catch fish, and — potentially — allow identification of individual whales by their unique vocal signatures.

There are roughly 870,000 miles of submarine cables globally, offering a vast existing infrastructure that could support acoustic monitoring and other ocean research if adapted appropriately.

“We think this has a lot of promise to fill in those key data gaps,” said Yuta Masuda, director of science at Allen Family Philanthropies.

In January, the High Seas Treaty takes effect and will establish safeguarded areas in international waters. Scientists say they need more detailed information about how human activities affect marine life so policymakers can prioritize regions that need protection most urgently.

On a barge near San Juan Island, the research crew joined cable sections while the vessel rolled on swells, streaming sensor data to shoreline computers as visual displays. Cameras were set to record whale movements whenever the system detected sounds. Testing will continue over the coming years before the technology can be used to guide protection plans for Salish Sea orcas.

Next steps: Continued trials will determine whether higher-frequency orca calls can be reliably detected and localized, how to integrate alerts with vessel operators, and how to scale the approach using existing submarine cable networks without disrupting communications infrastructure.