University of Vermont

Rubenstein Ecosystem Science Laboratory

CATOS projects

Champlain Acoustic Telemetry Observation System (CATOS): Our Projects

Lake Champlain offers a unique potential to study lake-wide fish movements using acoustic telemetry. The lake is ecologically similar to larger, harder-to-study systems with large commercial fisheries, such as the Laurentian Great Lakes, but its narrow profile permits coverage of a larger portion of the lake with a relatively small number of receivers. The potential to track fish movements throughout the lake will yield insights into season fish movements that are relevant to larger lakes.

Project 1: Lake Trout Spawing Site Utilization

Lake trout at spawning siteLake trout at spawning site.

Lake trout disappeared from Lake Champlain by 1900, though the causes of this disappearance are poorly understood. In 1972, the Vermont State Fish and Wildlife Service began a yearly stocking program in an effort to reestablish the natural population. Hatchery-raised lake trout survive in the lake, but have yet to produce viable young that grow into reproducing adults.

To understand why restoration has been an elusive goal, researchers must learn more about the mysteries of lake trout spawning behavior. Using CATOS, they are investigating the spawning movements of male and female lake trout within and among spawning seasons. So far, researchers have found that males are more abundant than females on spawning sites early in the spawning season and that lake trout return annually to the same sites. See map of receivers.

Project 2: Habitat Fragmentation and Movement

Causeway in Lake ChamplainCauseway in Lake Champlain

The impact of the 10 causeways in Lake Champlain on the movement and population dynamics of fish in the lake, and how or whether fish pass through the causeways between basins, is currently unknown. By using acoustic telemetry to track fish movements, researchers will conduct an exploratory study to investigate how Lake Champlain walleye use the corridors available to them.

Walleye are a highly mobile, coolwater species that are present throughout Lake Champlain. Due to their highly mobile nature, walleye are an ideal species to start exploring how fish use causeway corridors. Our goal is to tag walleye within each of the basins and observe their interactions with corridors and how these movements relate to lake stratification, resource allocation, and spawning migrations. See map of receivers.

Project 3: Long-Term Sentinel Rig & Detection Range

Diagram of sentinel rig with transmittersLong-term sentinel rig with transmitters moored at set distances from the receiver to measure changes in detection probability

To make strong inferences from telemetry data, the details of system performance under varying conditions must be thoroughly understood. The most important of these details is detection range. Detection range, as opposed to a set distance, is better defined as the relationship between detection probability and the distance of the transmitter from the receiver. Acoustic signals emitted by transmitters must travel through the organism’s environment and even in perfect conditions the signals are affected by spreading losses, refraction and attenuation.

When fish fitted with transmitters swim within the range of a receiver and remain there long enough for a transmission to be sent, probability of detection increases with increasing proximity to the receiver until the fish enters the minimum effective range, if one exists in a particular system.

By comparing these detection probabilities with the detection rates observed in fish, we will be able to infer that a fish was within a certain radius of a receiver. In addition, we will be able to compare our sentinel tag detection probabilities to meteorological data to investigate the degree to which detection probabilities are dependent on environmental parameters. This will inform a model that will project detection probability at a given distance based on the environmental conditions at the time in question.

Individuals interested in conducting acoustic tagging studies in Lake Champlain should contact Ellen Marsden at

Last modified April 06 2015 10:56 AM