Hydrophone diaries: eavesdropping on the soundscapes of the Salish Sea

Since 2023, Raincoast has been operating hydrophones to monitor underwater soundscapes in key locations. This relatively new initiative provides invaluable insights into marine environments while also presenting its fair share of challenges. As we’ve discovered, keeping underwater listening stations running smoothly requires a mix of ingenuity and perseverance!

Our Pender Whale Sanctuary listening station has been operating intermittently since August 2023. It is strategically located within an Interim Sanctuary Zone for endangered Southern Resident killer whales (SRKWs), areas designed to reduce vessel noise in critical foraging habitats. Through acoustic and visual monitoring, this station collects data on SRKWs’ exposure to vessel traffic, their use of the zone and underwater noise levels, as well as the presence of other marine mammals like Bigg’s killer whales, porpoises, and humpbacks. 

In June 2024, we expanded our hydrophone network with the addition of a Sunshine Coast listening station, filling a critical data gap in a region experiencing a dramatic resurgence of humpback whales since 2015. These whales are highly sensitive to underwater noise, making this an essential area for monitoring. The area is also used by Southern Resident killer whales during winter, when their need for undisturbed echolocation is vital for foraging for salmon.

Both stations will contribute to several research initiatives, including the collaborative “Singing to be heard” humpback whale study, led by Erin Wall, which investigates the impact of vessel noise on humpback song development, as well as a study led by Dylan Smyth on how underwater noise may affect killer whale vocalizations. 

NoiseTracker: Amplifying conservation efforts

We hope that the data from both stations will also contribute to the NoiseTracker project, a collaborative effort spearheaded by Raincoast to present real-time underwater noise levels across British Columbia and Washington State. By partnering with hydrophone operators along the coast and making this data accessible through a free, user-friendly platform, NoiseTracker will inform regulations, support conservation measures, and raise public awareness about the growing issue of underwater noise.

Trials and tribulations

If operating hydrophones has taught us anything, it’s that nothing under—or above—water goes as planned.

Take our Pender station, for example. The first hydrophone we installed worked beautifully… until it didn’t. Intermittent outages plagued the system, forcing us to upgrade to a new and supposedly improved hydrophone from the same company. This required rehiring a diver, and coordinating a redeployment mission…twice! Nature had other plans during our first attempt, unleashing a ferocious windstorm and powerful currents that forced us to call it off. Two weeks later we returned with the same diver, a healthy dose of optimism, and slightly less faith in weather forecasts – and finally succeeded. 

But just as we celebrated this victory, a new problem emerged: an annoying, persistent 60Hz AC “hum” that stubbornly sneaks into our recordings. Apparently, when your research site is land-based, electric interference can become your nemesis. We are now on a mission to vanquish the hum—ideally before it drives us to madness – or worse! Hydrophone operation and maintenance is a costly endeavor! 

Then there’s our Sunshine Coast station. After waging a predictable battle with the omnipresent AC hum (spoiler alert: it won round one), we finally achieved – for nearly two glorious months — recording perfection. The hydrophone operated beautifully, capturing rich recordings of marine life though periodically drowned out by vessel noise. Until one day…silence. Dead silence. We replayed the final recording, and what did we hear? Clues. The sounds of a boat dragging something, the occasional whine of an electric motor, and the rhythmic clunking of gear being loaded. Our prime suspect? A fishing boat, probably blissfully unaware that it was hauling off our hydrophone cables along with its catch of the day.

Now we are faced with two possibilities: either a diver can rescue and redeploy the existing hydrophone, or we’ll need to source and install an entirely new one. We’re crossing our fingers for the former while keeping our bank account on life support for the latter.

The truth is, hydrophone operation is not for the faint of heart—or wallet. Between dodging prawn boats and battling rogue electrical hums, we have learned that resilience is key. And despite the hiccups, this work is a constant reminder of why we do what we do: to understand and protect the animals that depend on healthy, quiet oceans. The data we are collecting are critical for advancing marine conservation.

Mission accomplished (for now)

And now, a glimmer of good news to share; just this morning, with expert guidance from the SMRU team via a video call, we successfully tackled the persistent AC hum on our Pender hydrophone! By adding a power filter and a ground loop isolator to the system, we’ve achieved clean recordings at last – a triumph both for our data processing needs and for creating a decent-sounding livestream for outreach and education.

Curious to hear what’s happening under the waves? Tune into our livestream to listen in and join us in celebrating this small but meaningful victory. Of course, you’ll hear some noise – not just from wind, currents, waves, and rain, which can be loud at times, but also from the constant rumble of vessel traffic.

Unlike the natural sounds of the ocean, vessel noise is a pervasive form of noise pollution that can drown out the many important sounds of marine life. But if you are lucky, you might just catch killer whales communicating or humpback whales practicing their song – a poignant reminder of what we are striving to protect. 

So, if you’ve ever wondered how to support whale recovery efforts while chuckling at our expense, donations are always welcome!

You can help

Raincoast’s in-house scientists, collaborating graduate students, postdoctoral fellows, and professors make us unique among conservation groups. We work with First Nations, academic institutions, government, and other NGOs to build support and inform decisions that protect aquatic and terrestrial ecosystems, and the wildlife that depend on them. We conduct ethically applied, process-oriented, and hypothesis-driven research that has immediate and relevant utility for conservation deliberations and the collective body of scientific knowledge.

We investigate to understand coastal species and processes. We inform by bringing science to decision-makers and communities. We inspire action to protect wildlife and wildlife habitats.