Abstract
Acoustic telemetry is an important tool for assessing the behavioural ecology of aquatic animals, but the performance of receivers can vary spatially and temporally according to changes in environmental gradients. Studies testing detection efficiency and/ or detection range are, therefore, important for data interpretation, although the most thorough range-testing approaches are often costly or impractical, such as the use of fixed sentinel tags. Here, stationary tag data (from study animals that had either died or expelled their tags) provided a substitute for the long-term monitoring of receiver performance in a wetland environment and was complemented by periodic boat-based range testing, with testing of the effects of environmental variables (water temperature, conductivity, transparency, precipitation, wind speed, acoustic noise) on detection efficiency (DE) and detection range (DR). Stationary tag DE was highly variable temporally, the most influential factors being water temperature and precipitation. Transparency was a strong predictor of DR and was dependent on chlorophyll concentration (a surrogate measure of algal density). These results highlight the value of stationary tag data in assessments of acoustic receiver performance. The high seasonal variability in DE and DR emphasises the need for long-term receiver monitoring to enable robust conclusions to be drawn from telemetry data.
Highlights
The application of acoustic telemetry to examining the space-use and behaviour of aquatic animals has grown exponentially in recent decades (Hussey et al, 2015)
Passive acoustic telemetry functions by transmission of coded ultrasonic signals between tags and submerged hydrophones coupled with receivers (‘receivers’ hereafter), which are usually positioned at fixed locations
Mean daily water temperature and total daily precipitation were retained in the bestfitting generalised linear mixed models (GLMM) predicting detection efficiency (DE), with both variables having a negative effect on the probability of detection (Table 3a; Fig. 3)
Summary
The application of acoustic telemetry to examining the space-use and behaviour of aquatic animals has grown exponentially in recent decades (Hussey et al, 2015). It has benefitted from rapid technological development (e.g. Klinard et al, 2019b; Reubens et al, 2019), resulting in a wealth of data to support species and habitat management (Brooks et al, 2019) in both the marine and freshwater environments (e.g. Davies et al, 2020). Assessments of how the performance of receivers varies over time and space have been less frequent (Kessel et al, 2014), risking the misinterpretation of animal behaviour if the frequency of acoustic detections do not directly represent the space-use and activity of tagged animals (Payne et al, 2010)
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