Telemetry is valuable for gaining understanding about of how a species interacts with its habitat over space and time. Submerged passive acoustic receivers are an increasingly popular technology that allows researchers to track numerous individuals over long periods of time continuously. Receivers anchored to the substrate detect and record the date, time, and unique ID of acoustic transmissions from tags attached to a species of interest. Acoustic signal strength naturally attenuates over distance, but is also affected by numerous variables. Knowledge of a receiver’s effective detection range is crucial for determining optimal receiver locations and accurately interpreting data, yet range-testing is often under-utilized and results rarely published. Buck Island Reef National Monument in the U.S. Virgin Islands is a fully protected marine park where researchers recently deployed a 52 receiver array to investigate the spatial ecology of several species. We submerged range-testing tags at various distance intervals in each cardinal direction from 19 array-representative receivers in order to understand how benthic structure, depth, wind speed, sea-surface temperature, and time of day affect the probability of detection at each receiver. Using a generalized linear mixed model, we analyzed the effects of the covariates on the probability of detection.
Results/Conclusions
The mean probability of detection 100 m away from a receiver across the entire array was 58.2% (95% CI: 44.0 – 73.0%) using the best supported model. At 200 m from a receiver predicted detection probability decreased to 26.0% (95% CI: 11.4 – 39.3) and at 500 m away it was only 0.2% (95% CI: 0.03 – 0.3%). Effective detection range or the distance at which 50 % of detections are successfully recorded was 213.4 m (95% CI: 198.5 - 221.8 m) in homogenous sand, 123.9 m (95% CI: 95.9 – 152.3 m) in low rugosity hard bottom, 83.7 m (95% CI: 36.5 – 142.7 m) in mixed hard bottom with sand channels, and 30.7 m (95% CI: 8.1 – 56.7 m) in high rugosity reef habitat. Using the best model to predict for receivers in the entire array based on habitat and depth showed a significant lack of coverage north of Buck Island. Coefficient estimates indicate a decrease in probability of detection at night, but long term sentinel tags are needed to investigate the relationship further. Our results provide insight into factors affecting detection ranges within a dynamic coral reef environment and provide a possible method for post receiver deployment range-testing.