Detection Range of Acoustic Receivers in a Large Hydropower Reservoir

Abstract

Acoustic telemetry manufacturers report estimated detection ranges under idealized conditions, but environmental conditions such as water depth, substrate type, and turbulence can affect the range of reliable detection. Range testing of low (Vemco V7 136 dB re 1µPa@1m) and high power (V13 147 dB re 1µPa@1m) acoustic transmitters (tags) was performed near a hydropower generating station and its associated reservoir using both active (mobile; VR100) and passive (stationary; VR2W/VR2Tx) receivers. Low power tags are typically used to track small fish such as juvenile Atlantic salmon (Salmo salar), whereas high power tags are typically used to track larger fish such as adult salmon. The results found herein were applied to concurrent salmon telemetry studies. Detection ranges of the low power tags were within 246-351 ± 20-70 m (mean ± SE), and the high power tags were within 537-1106 ± 53-272 m. Observed detection ranges were comparable or higher to manufacturer estimates for both tag types being detected by passive receivers, and were lower than expected for both tag types being detected by active receivers. Passive receivers were further tested by mooring a fixed sentinel tag (low power) on a receiver line at the hydropower site for 50 days. The sentinel tag detection range of 212 m was less than the expected range of 280-292 m, and was not found to be significantly impacted by wind speed. There was evidence of a hydropower effect on detection probability (up to 95% reduction) of both tag types for the active receiver, and detection ranges were significantly lower at the hydropower site than the reservoir site for the high power tag. The results of this study give insight to the initial design of acoustic telemetry studies beyond what can be gathered from manufacturer's estimates, but rather near hydropower facilities and within large reservoirs; however, detection ranges reported herein do not replace the importance of range testing in site-specific conditions.

WITHDRAWN: Receiver mount design, tag depth, and wind speed affect detection probability of acoustic telemetry tags in a Missouri River tributary

“…This was likely a function of discharge, as the V16 tags have a higher power (158 dB) than the V13 tags (147 dB). Higher tag power should result in increased detection distances (Babin et al 2019;Shultz et al 2021). Higher discharge can increase static noise in the system (Medwin and Clay 1997) and result in more debris in the river, which can lead to increased biofouling of receivers.…”

“…Wind induced noise may have had a greater in uence on V13 tags than V16 tags due to lower power output in the V13 tags. Higher tag power should result in increased detection distances (Babin et al 2019;Shultz et al 2021) and, therefore, higher detection probabilities. Wind-induced noise impacts a larger portion of the water column at shallower depths (Huveneers et al 2016), and because the river was shallower during the V13 trial, this may explain the lower detection of the deep V13 tags.…”

Overwintering and migration behaviour of post‐spawned Atlantic salmon Salmo salar in a large hydropower‐regulated river and reservoir

“…Detection range was defined as the distance whereby 50% of transmissions were reliably detected. Average detection ranges were 537–897 m (Babin et al ., 2019).…”

Acoustic telemetry detection probability and location accuracy in a freshwater wetland embayment

“…In that example, active tracking locations were compared to passive receiver detections of tagged fish within an array to estimate detection range [33]. More recently, detection probability was assessed for two different acoustic transmitters in a hydropower reservoir by allowing the active receiver to passively sample while gradually increasing distance from the known transmitter location until detection did not occur [34]. While the underlying questions differed from those in our study, it exemplifies the need to address detection probability in active tracking studies to aid in data interpretation [35].…”