Using VEMCO Tags to Identify Predation Events
When principal investigators Dr. Eddie Halfyard and Dr. Aaron Fisk of the Great Lakes Institute for Environmental Research at the University of Windsor wanted to better understand predation events in acoustic telemetry studies, they undertook a project to evaluate VEMCO’s new prototype predation tag.
In the past, attempts to identify predation in studies have relied on sensor data to differentiate predators and prey or have applied subjective criterion to what constitutes ‘normal’ prey behaviour.
“Unfortunately, these methods have limitations,” said Dr. Halfyard. “Sensor tags tend to be larger and are therefore not applicable to many species. They also may not clearly identify differences between predator and prey behaviour, and the approaches themselves rely heavily on what subjective decisions are being made.”
In an effort to address the issue of predation and permit objective evaluation of when predation occurs, VEMCO has developed a prototype predation tag capable of detecting predation events. Important considerations for the planning of acoustic telemetry projects and the interpretation of telemetry data are tagging effects (i.e. altered behaviour, swimming performance or mortality risk), limitations of the telemetry gear (i.e. detection efficiency), and that the data being collected represents the target animal.
“The latter is an important consideration because tagged animals are frequently consumed by predators,” noted Dr. Halfyard. “Under this scenario, the data collected by each telemetry year could potentially represent the movements and survival of predators and not the intended tagged prey species.”
The goals of the testing were threefold:
- To determine whether predation tags accurately detected when predation events occurred
- To determine the rate at which the predation tags falsely identified a predation event when no such predation event occurred (i.e. a false positive)
- To begin to examine the factors that influence the lag time between the predation event and when the tags report on the predation event.
“Early results show that VEMCO’s predation tags are a very useful tool for the identification of predation events and will provide increased confidence in telemetry results,” concluded Dr. Halfyard. “Further, the identification of spatial and temporal patterns in predation will permit addressing many questions related to trophic interactions.”
Dr. Halfyard also indicated that the tags are particularly well suited for short-term (i.e. 2 months) evaluation of survival and behaviour at cooler water temperatures (i.e. salmon smolts).
The work was supported by MITACS and conducted in collaboration with VEMCO at Leadley Environmental Inc., a partner of the University of Windsor.
Photo 1: Dr. Eddie Halfyard
Photo 2: Yellow perch after surgical implantation of a VEMCO prototype predation tag