Performance of a 307 kHz acoustic telemetry system in a small freshwater lake

Abstract

Abstract Background Acoustic telemetry is widely used to study the movements of aquatic animals, yet spatial and temporal variation in acoustic system performance can bias inferences if not properly accounted for. Here, we conducted the first field-based assessment of detection efficiency and range for Innovasea’s high-frequency acoustic telemetry system (HR3-307 kHz) in a 0.23 km 2 (max depth ~ 10 m) freshwater lake in Ontario, Canada using 10 stationary reference tags and internal synchronization (sync) tags from an array of 33 receivers. This system uses miniaturized tags that transmit at high rates (V3-1x: 1 transmission per 25–35 s; V6-4x: 1 transmission per 6–10 s), making them suitable for implantation in small-bodied fish and enabling fine-scale movement studies not previously possible with conventional 69 kHz systems. Results Hourly detection probability declined strongly with increasing distance from receivers, and differed by tag type, with the larger V6-4x tags exhibiting higher detection probabilities than the smaller V3-1x tags across longer distances. The distance at which single-transmission detection probability reached 50% (R50) was 55 m for V3-1x tags and 85 m for V6-4x tags. The transmission rates of these tags translate into high practical detectability, defined here as the cumulative probability of detecting a tag at least once within a given time window, with per-transmission R50 distances increasing substantially to 91–138 m for V3-1x tags and 262–330 m for V6-4x tags over 1- and 2- min intervals. Environmental variables, including wind speed and ambient noise, had small negative effects on detection efficiency, while water temperature and precipitation had negligible effects. Ice cover increased detection efficiency by ~ 3.5% compared to open-water conditions. Receivers (but not reference tags) varied slightly in their detection performance, suggesting an effect of local conditions. Conclusions These findings inform array design and data interpretation for studies using Innovasea’s new 307 kHz acoustic telemetry system to track fine-scale movements of small-bodied fish.