Detection range and efficiency of acoustic telemetry receivers in a connected wetland system

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.

Movements of common bream Abramis brama in a highly connected, lowland wetland reveal sub‐populations with diverse migration strategies

“…Data were downloaded every 3 months, while batteries were replaced annually. Detection range was highly variable according to local environmental conditions, but rarely fell below channel width distance (Winter et al, 2021). Distance measurements between receivers represented the mid‐channel circuitous river length.…”

“…Although the recovery of bream following acoustic tagging can be rapid (Le Pichon et al., 2015), all data collected in the first 7 days following tagging were excluded from analyses (in case the fish were demonstrating abnormal behaviours). Data were also excluded from stationary tags, which occurred due to fish death or tag expulsion within range of an acoustic receiver (Winter et al, 2021). The seasonal range of each fish in each season was estimated as the distance (in river km) between the furthest upstream and furthest downstream detections, and where this included two or more rivers, the distances were summed.…”

Dual‐isotope isoscapes for predicting the scale of fish movements in lowland rivers

“…Receivers were placed in the channel margins at approximately mid‐water depth. Detection ranges were variable, dependent on environmental conditions (Winter et al, in press ), however very rarely fell below channel width distance.…”

Taking the time for range testing: an approach to account for temporal resolution in acoustic telemetry detection range assessments

“…This relationship is subject to the transmitter-receiver distance, environmental conditions and technical features, in addition to the behaviour of the tagged animal itself. Environmental impacts include static features, such as habitat type and bottom depth [2,3], as well as system dynamics that vary over time, such as wind, water currents, precipitation, biogenic and anthropogenic noise, temperature and stratification [4][5][6]. The detection range can also be dependent on the specifications of the equipment used, including transmitter type, transmitting power output and transmitter placement [7][8][9], as well as receiver depth, orientation and deployment method [5,10,11].…”

“…This individual detection probability is estimated either for every single transmission [3,10,17], or as the probability of detecting a single transmission within a period of time (e.g. for a daily resolution, this represents the probability of detecting a transmission given that day's conditions) [5,6,18]. However, many telemetry analyses do not build on single detections as a response variable, but rely on a binary presence/absence metric within a specified time bin (e.g.…”