Passive Acoustic Monitoring in Freshwater Ecosystems: Beyond the Oceans
Listen to Life Beneath the Surface of Lakes and Rivers
With Passive Acoustic Monitoring (PAM), uncover the invisible impacts of human activity and climate change in freshwater ecosystems—non-invasively, accurately, and in real-time.
Though freshwater ecosystems make up less than 1% of Earth's water, they support over 100,000 species. These environments are now facing mounting threats—from pollution to climate change. PAM, originally developed for marine research, is expanding into rivers, lakes, and wetlands.
This tool enables scientists to monitor biodiversity and environmental changes by listening to the soundscape—without disrupting wildlife.
What Is Passive Acoustic Monitoring (PAM)?
PAM uses underwater microphones (hydrophones) to record sounds in aquatic environments. It helps detect species, track human disturbances, and monitor environmental health. Traditionally applied in ocean environments, it is now a vital tool in freshwater conservation—detecting fish, tracking invasive species, and capturing the effects of noise pollution from boats, dams, or industrial activity.
Why PAM Is Crucial in Freshwater Ecosystems
Freshwater biodiversity is collapsing: one in three species is at risk of extinction. PAM allows researchers to:
Track species presence and behavior using vocalizations
Identify areas affected by human noise (boating, dams, industry)
Monitor fish migrations and detect unsustainable fishing
Its non-invasive nature and cost-effective deployment make PAM ideal for long-term monitoring across vulnerable freshwater habitats.
Unique Challenges of Freshwater Acoustic Monitoring
Freshwater environments are smaller and shallower than oceans, with more complex sound propagation conditions. Seasonal temperature shifts, water depth, and vegetation all affect sound transmission.
As a result, researchers must carefully select sampling sites and calibrate equipment to capture high-quality data—especially in areas with high human interference.
Methods & Technologies Used in Freshwater PAM
Sensor Deployment Strategies
Fixed Installations
Mounted to piers, buoys, or lakebeds for long-term tracking
Mobile Platforms (AUVs/ROVs)
Collect wide-area sound data flexibly
Drifting Buoys
Cover vast areas in motion, ideal for open water
Towed Arrays
Sensors dragged behind vessels for spatial sound coverage
Types of Equipment
Hydrophones
These sensitive underwater microphones capture a wide range of frequencies, allowing researchers to monitor animal vocalizations, environmental noise, and human activities.
Recording Devices
Designed to store the captured sounds, recording devices can be tailored for short-term surveys or long-term studies, depending on the project’s scope.
Data Loggers
These tools continuously record sound levels, providing real-time insights or long-term datasets for studying changes in soundscapes and animal behavior over time.
Data Collection Techniques
Data collection in freshwater involves two main approaches: continuous monitoring and intermittent sampling. Continuous monitoring provides a constant stream of data, capturing every sound in the environment, which is especially useful for tracking low-frequency sounds and subtle changes in fish activity. Intermittent sampling, on the other hand, involves recording at specific intervals, offering a more efficient method for long-term studies when continuous tracking is not feasible.
The success of either approach depends heavily on on-site selection; placing sensors in areas with minimal human interference can help avoid low-quality data and ensure an accurate catch of fish sounds and environmental noise.
Impacts of Noise Pollution in Freshwater Ecosystems
Anthropogenic Noise Sources
Recreational boating, dam operation, construction, and industry increase sound levels.
In shallow, enclosed freshwater systems, noise cannot dissipate easily, magnifying its effects.
As climate change alters water levels and temperature, sound propagation is also affected.
Warmer waters change sound speed and disrupt frequency ranges critical for fish behavior
Shifting water levels challenge consistent data collection
These changes make PAM even more essential to understanding ecological shifts over time
Sinay's Acoustic Solutions for Freshwater and Marine Protection
Sinay's advanced Passive Acoustic Monitoring systems are designed to meet the specific challenges of both freshwater and marine ecosystems.
What We Offer:
PAM Buoys with broadband hydrophones detecting wide frequency ranges (including dolphin, porpoise, and fish vocalizations)
Real-time noise level mapping to assess impacts from boats, piling, and ports
Cloud-connected dashboards for easy access and data visualization
Compliance-ready methodology using BAG/BACI standards across project phases—from baseline to post-construction
Support for biodiversity protection and climate resilience strategies
Freshwater Needs Our Attention
Passive Acoustic Monitoring has proven itself beyond the oceans. By listening to rivers, lakes, and wetlands, PAM helps safeguard freshwater biodiversity against invisible threats. As global change accelerates, PAM offers science, industry, and conservation teams the insights they need to respond with precision and care.
"By listening to our freshwater ecosystems, we can protect what we cannot always see."
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