How Acoustic Telemetry Works

Many marine animals are in constant motion, migrate vast distances, and often inhabit murky or deep water. So how do we even observe them, let alone protect them?! In recent years, acoustic telemetry has emerged as powerful tool that FACT Network scientists are now using to better understand the behaviors and habitat needs of coastal fishes and sea turtles.

So what does acoustic telemetry even mean? This term simply refers to using sound (acoustics) to relay information across open space (telemetry). In our application, FACT researchers attach acoustic transmitters (or “tags”) to the fish or turtles they study. Each tag emits unique sound pulses that are heard and understood by our underwater tracking stations (receivers).  As animals swim through our network of over 900 tracking stations, their behavior is revealed!

Photo Caption: Acoustic receiver now monitoring a reef near Jupiter, Florida. Our FACT Network receivers are deployed in many different ways depending on location and habitat. These receivers can typically hear passing animals from 300 – 1000 meters away. Image Credit: Erick Ault

Acoustic tags come in a variety of styles and can last up to a decade. Some tags also contain sensors that relay environmental conditions such as water temperature and depth. In the FACT Network, tags are usually surgically implanted inside fish to increase retention, but are always externally attached to sea turtles.

A medium-sized acoustic transmitter with a 5-year battery life. Most transmitters in the FACT Network “ping” every 1-3 minutes. Image Credit: Erik Ault 

A transmitter being internally implanted into a common snook. Image Credit: Erik Ault                                                                                                                                    

Acoustic telemetry is just one technology now in the toolbox of marine scientists that study animal behavior. FACT members also commonly employ other technologies including a variety of satellite transmitters, Unmanned Underwater Vehicles (UUVs), Unmanned Surface vehicles (USVs), and inertial measurement units (IMUs) to reveal the movement and survival of sea turtles and marine fishes.


The Technology: Why We Collaborate

The foundation of our FACT Network is passive acoustic telemetry which relies on underwater tracking stations (acoustic receivers) to understand the movements of our tagged fish and sea turtles. This approach has gained favor in recent years because it dramatically extends the duration and distance we can follow animals, giving us new insights into habitat needs, seasonal migrations, and long term survival. This is information that has historically been difficult to collect, even for relatively well studied species.

Of course, the more tracking stations we have in the water, the more often we detect our animals. FACT partners recognize that collaboration allows us to take on bigger projects than if we were working individually. To that end, FACT members all deploy compatible equipment and exchange tag ID numbers. We meet twice yearly, share ideas and data analysis techniques. Most importantly, we freely exchange animal detections among ourselves and with other researchers working along the coast. It is now commonplace to observe the movements of tagged animals over hundreds of kilometers and for several years. The behavior of our region’s managed marine species are quickly coming into focus.