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Please read this page or click on the following links to learn more about the UVM/Rubenstein Ecosystem Science Laboratory Study, Champlain Acoustic Telemetry Observation System (CATOS):

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$50 Reward to Report Tagged Fish

Should you catch a tagged fish (trout, walleye), refer to “report a fish” page, where fishermen can fill out a form to report that they’ve caught a tagged fish. You may also send an email to with information about found tags. If the fish is in good shape and can be released, please do so! If not, simply save the acoustic transmitter that can be found in the fish’s abdomen and we will pick it up and reward the finder with $50.

Champlain Acoustic Telemetry Observation System (CATOS)

CATOS is a pilot study, pioneering the use of acoustic telemetry in Lake Champlain to explore what this exciting technology can do to benefit the local commercial and recreational fisheries and improve our understanding of lake ecology.

Fish Pinging Receivers561Acoustic telemetry is a technology that allows researchers to remotely track and study the behavior of fish that are implanted with transmitters. Receivers strategically placed throughout the study system collect data on each fish’s location every few minutes for up to three years. We are currently using this technology to study three main projects in Lake Champlain:

  1. Lake trout spawning site utilization
  2. Movement of fish in a fragmented habitat
  3. Detection range of acoustic receivers

Our overall goal is to establish an acoustic tagging infrastructure, the Champlain Acoustic Telemetry Observation System (CATOS), that can be utilized by multiple projects and investigators.

Map of Receivers (see map)

Our acoustic receivers are being used for ongoing studies of fish movement, species movement, and behavior. Placed strategically at 27 sites throughout Lake Champlain, these compact data-logging computers provide a tracking system for tagged species of interest and can be used for many additional projects.

What is Acoustic Telemetry? How It Works

Acoustic telemetry is a technology that allows researchers to remotely track the movements of the organism of interest. Study organisms are equipped with a transmitter that periodically emits acoustic signals, which are detected by receivers throughout the study area.


TransmitterIn this study, fish are equipped with acoustic transmitters (tags) that are individually coded, have a 3-year battery life, and are set to transmit a signal with their identification number and a timestamp every 60-180 seconds. That means when a tagged fish swims within the range of a receiver, the receiver detects an acoustic signal (a “ping”) from the tag, and records the tag’s identification number and the time that it was detected. The “pings” are sent out every 2-3 minutes over the course of 3 years!

With such high resolution data, this technology can be used to address a variety of questions, and can be used for any species that can handle tag attachment or implantation without an effect on their behavior.

Implanting transmitters

Inserting TransmitterIn order to track the movement of certain organisms, individuals must be surgically implanted with acoustic transmitters. To prevent a fish from being negatively impacted by the burden of the tag, the tag must be no more than 2% of the fish’s body weight.

Fish are captured by trap net or gillnets set for 1-2 hours to ensure minimal stress and injury. Once the fish are removed from the nets and anesthetized, a 2-3 cm incision is made on the abdomen of the fish and the tag is inserted (incision size and placement varies with the fish and tags being used, but the size of the incision is large enough to allow tag insertion without tearing tissue).

The fish is then sutured and placed in a recovery tank until they have fully regained equilibrium and swimming ability. The fish is also fitted with an external tag using a standard tagging gun, identifying the fish to anglers and providing contact information in order to report finding a tagged fish.


Receivers are strategically placed at constriction points throughout Lake Champlain (see map) in order to detect the movement of certain fish species. Receivers are held in place by buoy systems secured by 100-pound concrete anchors and held 3m off the bottom by subsurface buoys. Surface buoys mark these rigs in the fall, summer and spring, and are removed before the water freezes in the winter. Data gathered by the receivers are downloaded twice a year, in the late fall and early spring.

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