How underwater fiber-optic cables can be transformed to monitor killer whales

American scientists are working to repurpose the vast network of fiber-optic cables that lie across the world’s ocean floors, hoping to transform them into a massive underwater listening system capable of capturing the clicks, calls, and whistles of whales. By turning these cables into a continuous oceanwide microphone, researchers aim to gather data on how whales respond to ship traffic, food scarcity, and climate change.

If successful, the thousands of miles of existing undersea fiber-optic cables could become part of a global acoustic monitoring system that would revolutionize marine conservation, according to an article on this venture by AP.

The technology enabling this, known as Distributed Acoustic Sensing (DAS), was originally developed for industrial use — to monitor pipelines and detect faults in infrastructure. Now, a team from the University of Washington is adapting it to listen beneath the waves.

Unlike traditional hydrophones that record from a single location, DAS turns the entire cable into a series of sensors capable of tracking the movements of marine life.

“We can imagine that we have thousands of hydrophones along the cable recording data continuously,” said Shima Abadi, professor at the University of Washington Bothell School of STEM and the University of Washington School of Oceanography. “We can know where the animals are and learn about their migration patterns much better than hydrophones.”

The researchers have already tested the method successfully with large baleen whales. During an experiment off the Oregon coast, they recorded the low-frequency calls of fin whales and blue whales using existing telecommunications cables on the seabed.

However, applying the technology to orcas presents new challenges. Their vocalizations occur at much higher frequencies — a range the system has yet to be tested for.

According to the article, the Southern Resident orcas that inhabit the Salish Sea are endangered, with their population holding steady at around 75 individuals. These whales face three major threats: underwater noise, toxic pollutants, and a shortage of food.

“We have an endangered killer whale trying to eat an endangered salmon species,” said Scott Veirs, president of Beam Reach Marine Science and Sustainability, a nonprofit developing open-source acoustic tools for whale conservation.

The Chinook salmon that the orcas depend on have declined sharply — their numbers have dropped by 60% since 1984, according to the Pacific Salmon Commission, due to habitat destruction, overfishing, dam construction, and climate change.

Orcas rely on echolocation — bursts of rapid clicks that bounce off objects — to find salmon in murky waters. But the increasing noise from ship traffic can drown out these signals, making it harder for them to hunt and communicate.

If DAS proves successful, it could give scientists the ability to track whales in real time and implement immediate protective measures. For example, if the system detects a pod of orcas moving south toward Seattle and estimates their speed, researchers could notify Washington State Ferries to temporarily slow down or delay noisy operations until the whales have passed.

“It will for sure help with dynamic management and long-term policy that will have real benefits for the whales,” Veirs said.

By Nazrin Sadigova