Environmental interference factors affecting detection range in acoustic telemetry studies using fixed receiver arrays

Abstract

Historically, acoustic telemetry studies tracking movement of aquatic organisms have lacked rigorous, long-term evaluations of detection range. The purpose of the present study was to identify potential sources of variability in long-term acoustic telemetry data, focusing specifically on environmental variability. The study was conducted for 15 mo in Gray's Reef National Marine Sanctuary, Georgia, USA, using 2 submersible Vemco VR2W hydrophone receivers and 2 stationary range test transmitters (controls). Tag detections (±1 SE) decreased from 54.2 ± 2.5 to 11.4 ± 0.5 detections d −1 as transmission distance increased from 100 to 300 m. Detections varied seasonally (likely due to stratification), with the direction of flood and ebb tidal currents (12.4 h cycle), and with tidal current speed (6.2 h cycle). Tides explained up to 92% of the short-term variability in hourly detection data. Detections also increased or decreased during episodic weather events depending on the season and type of event. These results suggest that stationary control tags are useful for characterizing variability in sound transmission in open water marine acoustic telemetry studies.

Factors affecting detection efficiency of mobile telemetry Slocum gliders

“…5). This is generally in line with previous studies [3][4][5]. We suspect more studies are necessary during highly stratified periods to estimate the full impact of a stratified water column on acoustic detection efficiency, as stratification played only a minor role in detection efficiency for the VMT.…”

“…Detection efficiency of the VMT and integrated VR2c's differed depending on the distance between the receiver and transmitter. At 0.1-0.2 km, the detection efficiencies of the VMT and VR2c receivers were near 30-40%, which is similar to the mean detection efficiency (33%) reported by fixed arrays in a shallow coastal ocean [3]. However, our detection efficiency was much lower than the 80-90% detection efficiency by high-power tags reported by arrays in an Arctic embayment, fresh water lake, and a subtropical marine reef [25].…”

“…These gliders encountered three prolonged wind events >10 m s −1 (Fig. 3a), presumably changing the subsurface noise conditions [3]. Stratification of the water column is most pronounced early in the mission, with up to a 4 sigma (4 kg m −3 ) difference in density between surface and bottom waters.…”

“…The detection range of acoustic receivers depends on in situ listening conditions, which are linked to environmental conditions. Tides, currents, winds, stratification, and listening array configuration can impact detection efficiency, thus impacting the study of the presence and movement of organisms using acoustic biotelemetry [3][4][5].…”

Fine-scale movement, activity patterns and home-ranges of European lobster Homarus gammarus

“…1), 4 m above the seafloor. A V13 synchronisation tag (synctag) was moored on the seafloor beneath each receiver to allow for characterisation of variability in detection rates (Mathies et al 2014) and for post-hoc correction of clock drift (Andrews et al 2011). Individual surface markers were attached to a second weight, connected to receiver-weights via a 50 m bottom-line, ensuring receiver movement was limited.…”