Acoustic telemetry: an indispensable tool for monitoring aquatic species

2024-01-08 Updated: 2024-01-18

Photo: Fisheries and Oceans Canada

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Technological advancements over the last few decades have changed the way researchers monitor wildlife species. Satellite tracking, for example, has rapidly become an indispensable tool for obtaining data on animal movements, reproduction, and survival.

While very effective on land, satellite tracking does not work underwater, as satellite waves cannot penetrate the surface. Other inventive techniques were devised to track the movements of fish, sharks, and invertebrates such as lobsters, sea urchins and sea cucumbers, in their natural environments. One such technique is acoustic telemetry, a method based on the transmission of a signal coming from an acoustic transmitter implanted in a living organism.

A delicate operation

There are several methods for fitting animals with acoustic transmitters. In the case of fish, the transmitter is most often implanted in the abdominal cavity during surgery under anesthesia. The weight of the transmitter is generally between 2 and 5% of the fish's total weight to avoid altering its natural movements. In crustaceans, the transmitter may be glued to the shell, while in some marine mammals, it may be affixed to the animal's coat.

_{Photo: Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs}

The transmitter operation is simple. For striped bass, for example, the fish's transmitter sends an acoustic signal every 90 seconds to the nearest recording device, called the receiver. This signal is recorded and provides the fish's unique tracking number, as well as the date and time of its passage. By compiling the detections received by all the receivers, scientists can trace the movements of aquatic species.

An extensive network

American Eel, Striped Bass and Atlantic Salmon are among the 20 fish species studied by the Ministère de l'Environnement, de la Lutte contre les changements climatiques, de la Faune et des Parcs (MELCCFP) and Fisheries and Oceans Canada (DFO) as part of the monitoring of species at risk or exploited by sport and commercial fishing, a project of the St. Lawrence Action Plan. These departments have more than 420 receivers scattered throughout the St. Lawrence River, from Montreal to the Gaspé Peninsula, to carry out this monitoring.

In November, at the end of the season, the receivers are retrieved by the teams and the data is uploaded by the scientists to the collaborative Ocean Tracking Network (OTN) site, which offers, among other services, public access to various project visualization tools, news and scientific articles.

Future prospects

Thanks to all the data collected, scientists and their partners are able to share their knowledge, and monitor species over a wider area, and help ensure their long-term survival in a changing ecosystem.