Section 6. Underwater noise in British Columbia

Why underwater noise is a major issue in British Columbia

British Columbia’s coastal waters support an exceptional diversity of marine life while also hosting some of the busiest marine transportation corridors in the world. The convergence of international shipping, ferry traffic, industrial development, military activity, and intense seasonal recreational use has made underwater noise a defining feature of many BC marine environments. As a result, the province has become a focal region for both scientific research and policy discussions on ocean noise.

BC-specific contributors to underwater noise

Commercial shipping in BC waters

British Columbia lies along the Trans-Pacific shipping corridor linking Asia to North America. Major routes serving the ports of Vancouver and Prince Rupert pass directly through ecologically important areas, including the Salish Sea. High vessel traffic density means that low-frequency ship noise is present much of the time, elevating background sound levels well above natural conditions across large spatial scales.

Anchored vessels also contribute significantly to underwater noise in BC, particularly in port approaches and designated anchorage areas, where generators and onboard machinery can create persistent, localized sound sources.

Passenger vessels and ferries

British Columbia operates one of the largest ferry systems in the world, with over 35 vessels serving 47 terminals along the coast. These ferries generate consistent, predictable noise as they travel fixed routes multiple times daily. 

While individual ferries are generally quieter than large cargo ships, their frequency and proximity to shore mean that coastal habitats experience repeated disturbance. 

Seasonal cruise ship traffic further amplifies noise levels, especially along narrow waterways such as the Inside Passage, where sound can be constrained and propagated over long distances.

Recreational boating pressure

British Columbia is one of Canada’s most popular recreational boating destinations, with intense seasonal boat traffic concentrated in the Gulf Islands, Howe Sound, and coastal areas around Vancouver Island. During summer months, this traffic increases dramatically. While individual recreational boats are generally quieter than large commercial vessels, their cumulative effect can substantially raise noise levels in biologically important areas, including foraging habitat used by whales and salmon.

Industrial development and large infrastructure projects

Large-scale marine infrastructure projects in British Columbia have the potential to substantially increase underwater noise in some of the most ecologically important marine habitats on the coast. Of particular concern are projects that intensify vessel traffic in areas designated as critical habitat for the endangered Southern Resident killer whales (SRKWs).

Roberts Bank Terminal 2 (RBT2)

This federally approved port expansion would take place directly within the legally protected critical habitat of endangered Southern Resident killer whales. This transboundary region of the Salish Sea is essential for foraging, social cohesion, and calf rearing, all of which depend heavily on sound for communication and echolocation.

The Roberts Bank Terminal 2 expansion will lead to a substantial increase in large commercial vessel traffic through already noisy waters. Increased shipping activity raises background noise levels and intensifies acoustic masking, reducing the whales’ ability to detect prey, maintain contact with group members, and coordinate foraging. These impacts directly conflict with recovery objectives that identify quieter waters, reduced disturbance, and improved access to Chinook salmon as essential conditions for the survival of this population.

Scientific assessments and recovery plans have repeatedly emphasized that SRKWs remain at a high risk of extinction. Additional chronic noise associated with RBT2 risks further degrading acoustic habitat and undermining recovery efforts already strained by prey limitation and cumulative human pressures.

Read more about the RBT2 expansion and its implications for species at risk here.

Trans Mountain Expansion Project (TMX)

The Trans Mountain Expansion Project (TMX) began commercial operations on May 1, 2024, and has become another significant source of increasing vessel noise in endangered Southern Resident killer whale habitat. The expansion was projected to result in a seven-fold increase in oil tanker traffic from the Westridge Marine Terminal in Burnaby (from approximately 60 oil tankers per year to more than 400 annually) transiting through the Gulf Islands and the Strait of Juan de Fuca en route to the open ocean.

The dramatic increase in tanker traffic associated with TMX adds persistent low-frequency noise to core SRKW foraging areas, compounding existing acoustic stressors. Recovery strategies have clearly identified vessel noise reduction as a priority, yet the scale of additional traffic associated with TMX risks overwhelming mitigation efforts.

In particular, increased shipping from both the Trans Mountain terminal and port expansion projects like RBT2 threatens to erode or eliminate the benefits of voluntary vessel slowdown initiatives, such as those coordinated through the ECHO Program. As a result, there may be little to no net improvement, and potentially a worsening, of acoustic conditions for endangered whales, despite demonstrated benefits of slower vessel speeds.

Read more about TMX and unmet federal commitments to endangered whales here.

Military and government activities

Naval training exercises and sonar use in BC waters contribute episodic but sometimes intense underwater noise in parts of BC waters. While these activities are intermittent, their acoustic footprint can extend over large areas and add to the cumulative soundscape experienced by marine life.

Underwater noise threatens the recovery of endangered Southern Resident killer whales

The Southern Resident killer whales (SRKW) represent one of the most studied and concerning cases of underwater noise impacts on marine life. With only 74 individuals remaining as of 2025 (Centre for Whale Research), these endangered whales face imminent threats to their survival, and underwater vessel noise has been identified as one of the primary factors contributing to their decline, along with prey availability and contaminants. 

The science behind SRKW noise impacts

Southern Resident Killer Whales are particularly vulnerable to underwater noise due to their unique biological and behavioural traits. As fish specialists that rely almost exclusively on Chinook salmon, they depend heavily on echolocation to forage. Their acoustic behaviour is finely tuned to detect and capture salmon in the complex underwater environment of the Salish Sea.

Research has shown that vessel presence and associated underwater noise significantly impact Southern Residents in their summer range within Washington’s inland waters and British Columbia’s southern coastal areas, which serve as critical foraging habitat (NOAA Fisheries, 2024). Vessel noise overlaps with the frequency ranges used by these whales for echolocation and communication, directly interfering with their ability to locate prey and maintain acoustic contact with group members. A recent study found that ferries and cargo vessels were the main contributors of anthropogenic noise, and that anchored cargo vessels were the fourth-ranked contributor to this noise; tugs, fishing vessels and recreational vessels (whale watching boats, sports fishing boats, etc.) were found to contribute significantly to masking within SRKW communication bands (MacGillivray et al., 2025).

Masking effects on echolocation and communication

Southern Resident killer whales produce echolocation clicks at frequencies typically ranging from 15-25 kHz, with some energy extending up to 100 kHz. They also rely on a complex vocal communication system, including calls, whistles, and burst-pulse sounds, primarily in the 1-20 kHz range. Vessel noise overlaps with these critical frequency bands and causes acoustic masking, which interferes with the ability to echolocate and communicate. Fishing and recreational vessels contribute substantially to this masking, particularly during the busy summer months when vessel traffic peaks (Joy et al., 2019). Studies using acoustic tags attached to individual whales have revealed that Southern Residents must modify their vocal behaviour in response to vessel noise, calling more frequently and at higher amplitudes when boats are nearby (Holt et al., 2021).

Foraging impacts and energy consequences

For Southern Resident orcas, underwater noise results in lost foraging time, reduced food intake, and impaired communication during coordinated hunting. These impacts are particularly concerning given the whales’ reliance on echolocation to hunt Chinook salmon, and the additional pressure of declining salmon populations.

Researchers have used suction-cup acoustic and movement tags (DTags) temporarily attached to individual killer whales to observe their underwater behaviour in detail.This work has shown that vessel noise disrupts every phase of a foraging attempt – from searching for prey, to pursuing it, to making the catch. Whales made fewer prey capture dives and spent less time in them when vessels were within approximately 400 yards ( 366 metres), with females more likely than males to abandon foraging altogether at close vessel distances (Holt et al., 2021a). When nearby vessels emitted navigational sonar at frequencies overlapping with killer whale echolocation, whales made longer, slower dives to capture prey – and descended faster when noise levels were higher and vessels were closer, consistent with a vertical avoidance response (Holt et al., 2021b).

A study examining both Northern and Southern Resident killer whales quantified these effects across a broad range of noise conditions (Tennessen et al., 2024). Key findings included:

• Whales searched harder but caught less. For every 1 dB increase in received noise, the likelihood of searching behaviour increased by 4%, while the likelihood of successfully capturing prey decreased by 12.5%.
• Females were disproportionately affected. In noisy conditions, females were far less likely to pursue prey once detected – an effect not seen in males.
• At the highest noise levels, foraging nearly collapsed. Almost all deep foraging attempts recorded when noise exceeded 110 dB re 1 μPa resulted in failed prey capture.

These responses are consistent with auditory masking (see acoustic masking, above) – vessel noise interfering directly with the whales’ ability to detect and track prey through echolocation. For females, who bear the costs of pregnancy and lactation and give birth only every 3–7 years, foregoing foraging in the presence of vessels carries especially heavy consequences for a population of only 74 individuals.just missing a meal; she may be compromising her ability to sustain a pregnancy or nurse a calf.

Physiological stress responses

Chronic exposure to vessel noise has been linked to measurable physiological changes in Southern Resident killer whales (Ayres et al, 2012). Scientists have documented elevated stress hormone levels in whale feces, indicating that the acoustic environment is triggering chronic stress responses. This chronic stress can:

• Suppress immune system function, making whales more susceptible to disease
• Reduce reproductive success and calf survival rates
• Increase energy expenditure, exacerbating the impacts of reduced prey availability
• Affect cognitive function and decision-making

Family structure and social learning

Southern Resident killer whales live in complex matrilineal societies where acoustic communication plays a crucial role in maintaining family bonds and transmitting cultural knowledge (Ford J., 1989). Vessel noise disrupts these essential social interactions, potentially affecting:

• The ability of mothers to maintain contact with their calves
• Cultural transmission of hunting techniques and salmon knowledge
• Coordination of group hunting strategies
• Long-distance communication between family groups

Vessel traffic patterns in SRKW habitat

Monthly-average sound pressure levels from vessels consistently exceed wind-driven ambient sound by more than 10 dB throughout most of the Southern Resident killer whale habitat (Joy et al., 2019). This means that vessel noise has become the dominant acoustic feature of the whales’ environment, fundamentally altering the natural soundscape in which they evolved to navigate.

The problem is particularly acute in key areas, including:

• Haro Strait: a primary summer feeding area that serves as a major shipping corridor
• Boundary Pass: an important travel route for whales that intersects with heavy vessel traffic
• Rosario Strait: critical foraging habitat that experiences high levels of recreational boat traffic
• Puget Sound: winter habitat areas affected by port activities and ferry traffic

Case Study: Listening to the Salish Sea – what underwater microphones in Boundary Pass are telling us

To understand what vessel noise means in practice for Southern Resident killer whales, acoustic data from two hydrophone sites within Boundary Pass were analyzed by SoundSpace Analytics. Both sites sit within one of the busiest commercial shipping corridors on Canada’s Pacific coast and critical habitat for Southern Resident killer whales: Monarch Head on Saturna Island, where SIMRES has operated a hydrophone continuously since 2014, and a Raincoast hydrophone site near Wallace Point on the western side of Pender Island, listening out towards Haro Strait and Swanson Channel.

Together, these two datasets offer complementary perspectives: the Saturna record spans nearly a decade and reveals how conditions have changed over time, while the Pender data provides a higher-resolution snapshot – including the ability to track noise conditions minute by minute as individual vessels pass and whales vocalize nearby.

Noise trends at Saturna Island: a decade of listening

Acoustic data from the Monarch Head hydrophone across three years (2017, 2023, and 2025) reveal a striking and troubling picture of how vessel noise has changed over time in this critical corridor. Three complementary metrics are used to tell this story: Quiet Time (the percentage of time with no detectable vessel noise), Excess Noise (how much vessel noise elevates natural background sound levels, in decibels), and Listening Space Reduction (the percentage of acoustic habitat lost to vessel noise masking).

Quiet Time

The first measure is simply: how often is it quiet? Each loop in the figure below represents one year of data. The size of the loop shows how much quiet time existed – how often the hydrophone recorded no detectable vessel noise at all. In 2017, the loop was large, particularly during nighttime hours. By 2023 and 2025, the loops had compressed dramatically. Vessel noise is now present for the overwhelming majority of hours in the day, across every season of the year.

Excess noise

Even when vessels are present, their impact on the soundscape depends on how much they raise noise above natural background levels. This elevation – called Excess Noise – is measured in decibels (dB) above what the ocean would sound like without vessel traffic. Because the decibel scale is logarithmic, even a few additional decibels represent a substantial increase in acoustic energy. The figures below show how this vessel-driven noise elevation has changed between 2017 and 2025 – the first and most recent years of consistent monitoring at this site. In 2017, excess noise in the killer whale communication band typically reached 2–4 dB above natural levels. By 2025, that figure had nearly doubled, reaching 5–6 dB across most hours of the day.

Listening space reduction

The most direct measure of what vessel noise means for Southern Resident killer whales is Listening Space Reduction (LSR) – the percentage of acoustic habitat lost because vessel noise is loud enough to mask sounds the whales depend on. Think of it as the acoustic equivalent of a thick fog descending over the whales’ world: sounds that would normally carry over long distances are smothered, reducing the space within which whales can hear each other, detect prey, and navigate.

 The figures below show LSR across every hour of the day and every month of the year, for 2017, 2023, and 2025. In 2017, losses were moderate, concentrated during daytime hours in spring and summer . By 2023, LSR had intensified dramatically across nearly every hour and month of the year. In 2025, conditions remained severe, with little meaningful improvement. 

The acoustic data show that conditions at Monarch Head had already deteriorated significantly by 2023, before TMX began commercial operations in May 2024. The trends presented here therefore reflect a worsening baseline, to which TMX-related tanker traffic adds further pressure.

Commercial vessel traffic through Boundary Pass grew substantially over the monitoring period, and the Trans Mountain Expansion Project, projected to increase oil tanker traffic through the Gulf Islands and Strait of Juan de Fuca by as much as seven-fold, has accelerated that growth. The 2025 data presented here suggest that trajectory is already underway

A closer look: Pender Island 

A second hydrophone, operated by Raincoast near Wallace Point on the western side of Pender Island, listens out towards Haro Strait and Swanson Channel – just across the water from the Saturna monitoring site. Acoustic data from this instrument were analyzed by SoundSpace Analytics.

Although the Pender dataset covers a shorter period (October 2023 to February 2025), it captures the same essential reality: vessel noise is a constant and pervasive presence in these waters, not just during the busy summer months but throughout the year.

The figures below offer three complementary windows into the Pender Island soundscape: a summer overview showing the dramatic day-night rhythm of vessel noise, a seasonal comparison of diurnal noise patterns, and a detailed January 2025 analysis – including one memorable afternoon when a Bigg’s killer whale was detected near the hydrophone.

How are scientists working to tackle underwater noise in BC?

British Columbia has become a global leader in developing innovative approaches to understand and reduce underwater noise impacts on marine life. The urgency surrounding SRKW conservation has catalyzed unprecedented collaboration between government agencies, researchers, Indigenous communities, and industry.

ECHO – The voluntary vessel slowdown program

One of the most significant noise reduction initiatives in BC waters has been the Enhancing Cetacean and Habitat Observation (ECHO) voluntary vessel slowdown program in Haro Strait and Boundary Pass, which are key SRKW feeding areas. 

The Port found that, with over 80 percent of large vessels participating in the slowdown in 2022, underwater sound intensity in the area decreased by as much as 55 percent (ECHO Annual Report, 2022). This demonstrates that practical solutions can be highly effective when implemented with industry cooperation.

However, the voluntary nature of the program is also its key limitation. Participation cannot be guaranteed, and non-participation is often driven by legitimate safety constraints – such as weather, tides, and traffic conditions – that cannot be removed by policy alone. As a result, ECHO cannot be relied upon as a substitute for enforceable noise reduction requirements, nor as a mechanism to offset the acoustic effects of new or expanding vessel traffic. What the program demonstrates clearly is the potential of vessel slowdowns as a tool – and the need for regulatory frameworks that make such measures durable, mandatory, and comprehensive.

Comprehensive monitoring networks

BC researchers have established extensive passive acoustic monitoring networks throughout the region’s waters. These systems continuously record underwater soundscapes, allowing scientists to:

• Track changes in noise levels over time
• Identify specific noise sources and their impacts
• Evaluate the effectiveness of mitigation measures
• Provide real-time information to vessel operators about marine mammal presence

The BC Hydrophone Network is one such initiative, which aims to collect acoustic data on a coast-wide level, and calculate standardized noise metrics which can be used to inform decision-making. Some of these hydrophone datasets are publicly available on the Whalesound dashboard.

Collaborative research initiatives

The complexity of underwater noise requires interdisciplinary collaboration. Researchers are working with:

• Indigenous Communities: Incorporating traditional ecological knowledge with modern acoustic science
• International Partners: Sharing data and techniques with researchers in Washington State, Alaska, and other regions with similar challenges
• Industry Stakeholders: Developing practical noise reduction technologies that can be implemented on commercial vessels
• Conservation Organizations: Translating research findings into effective advocacy and policy recommendations

New technologies

The search for technological solutions to underwater noise is advancing rapidly, with several promising approaches being tested in BC waters:

Quiet ship technologies: New propeller designs to reduce propeller cavitation noise, hull modifications, and engine mounting systems can significantly reduce the noise that ships generate.

Bubble curtain systems: Air bubble systems that can reduce either machinery noise or propeller cavitation noise are being refined for commercial applications.

Real-time whale detection: A growing suite of technologies is being used to detect whales in real time and reduce the risk of acoustic disturbance. Advanced hydrophone arrays and AI-powered analysis can alert ships to the presence of marine mammals, allowing for immediate noise reduction measures such as speed reductions

In addition, infrared (thermal) camera systems are now being tested along the BC coast to detect whales at the surface based on body heat, even at night or in foggy conditions. These systems can identify whale blows and surfacing animals in real time and relay that information to vessel operators, providing an additional, non-acoustic layer of detection that complements hydrophone-based systems. When integrated with vessel traffic management, infrared detection has the potential to support proactive speed reductions and routing decisions that reduce both collision risk and underwater noise exposure.

What can individuals do about underwater noise in BC?

Whether you are a boater or a concerned citizen, there are numerous ways to help reduce ocean noise. 

As a vessel owner, operator, or marine engineer, you can:

SLOW DOWN – Simply slowing down will reduce vessel noise, the risk of collision with marine species, and lower fuel consumption.

TURN OFF – Echosounders and fish finders use sound waves to detect depths and objects. Turn them off when not in use.

MAINTAIN – Maintain clean hulls and propellers to reduce drag and cavitation. 

DESIGN & TECHNOLOGY – Incorporate new designs in vessels or retrofit old ones with quieter equipment, such as propeller blades with reduced cavitation, smaller and less noisy engines, and efficient hull designs.

GIVE SPACE – The further away noise sources are from an animal, the less the impact. Alter routes when marine mammals are in the immediate vicinity. Familiarize yourself with the local marine wildlife laws and guidelines.

As a concerned citizen, you can: 

CHOOSE – Individual decisions in our everyday lives can help lower ocean noise. Purchase less and locally to reduce shipping, reduce energy consumption, or opt for land-based marine wildlife options, such as using the BC Whale Trail.

RAISE YOUR VOICE – Voice your concerns with local government and decision-makers and vote for policies protecting marine ecosystems.

SPREAD AWARENESS – Highlight underwater noise with others and help start a movement.

The more people who understand and care about ocean noise, the more potential there is to create positive changes to support a healthy marine environment.This free course by the Marine Education and Research Society (MERS) can help keep you and wildlife safe while on the water. You can learn more about it here.