Abstract
Advances in acoustic telemetry technology have led to an improved understanding of the spatial ecology of many freshwater and marine fish species. Understanding the performance of acoustic receivers is necessary to distinguish between tagged fish that may have been present but not detected and from those fish that were absent from the area. In this study, two stationary acoustic transmitters were deployed 250 m apart within each of four acoustic receiver lines each containing at least 10 receivers (i.e., eight acoustic transmitters) located in Saginaw Bay and central Lake Huron for nearly 2 years to determine whether the probability of detecting an acoustic transmission varied as a function of time (i.e., season), location, and distance between acoustic transmitter and receiver. Distances between acoustic transmitters and receivers ranged from 200 m to >10 km in each line. The daily observed probability of detecting an acoustic transmission was used in simulation models to estimate the probability of detecting a moving acoustic transmitter on a line of receivers. The probability of detecting an acoustic transmitter on a receiver 1000 m away differed by month for different receiver lines in Lake Huron and Saginaw Bay but was similar for paired acoustic transmitters deployed 250 m apart within the same line. Mean probability of detecting an acoustic transmitter at 1000 m calculated over the study period varied among acoustic transmitters 250 m apart within a line and differed among receiver lines in Lake Huron and Saginaw Bay. The simulated probability of detecting a moving acoustic transmitter on a receiver line was characterized by short periods of time with decreased detection. Although increased receiver spacing and higher fish movement rates decreased simulated detection probability, the location of the simulated receiver line in Lake Huron had the strongest effect on simulated detection probability. Performance of receiver lines in Lake Huron varied across a range of spatiotemporal scales and was inconsistent among receiver lines. Our simulations indicated that if 69 kHz acoustic transmitters operating at 158 dB in 10–30 m of freshwater were being used, then receivers should be placed 1000 m apart to ensure that all fish moving at 1 m s−1 or less will be detected 90% of days over a 2-year period. Whereas these results can be used as general guidelines for designing new studies, the irregular variation in acoustic transmitter detection probabilities we observed among receiver line locations in Lake Huron makes designing receiver lines in similar systems challenging and emphasizes the need to conduct post hoc analyses of acoustic transmitter detection probabilities.
Highlights
Advances in acoustic telemetry technology have led to an improved understanding of the spatial ecology of many freshwater and marine fish species
More than 1.9 million acoustic transmissions were detected from eight stationary acoustic transmitters on 69 acoustic receivers set within four lines in Saginaw Bay and Lake Huron from November 2010 to November 2012 (Fig. 1; Table 1)
Short-duration preliminary range testing at limited spatial and temporal scales may not capture variation in acoustic transmitter detection probability observed at large spatiotemporal scales
Summary
Advances in acoustic telemetry technology have led to an improved understanding of the spatial ecology of many freshwater and marine fish species. Recent advances in acoustic telemetry technology and methodology have improved understanding of fish movements at spatial and temporal scales that were previously not possible and have provided insights into fish habitat use, spawning, site fidelity, and migration [5,6,7,8]. The distance between an acoustic transmitter and receiver in which an acoustic transmission can be detected depends on abiotic and biotic variables that influence the rate of energy attenuation as the signal passes through the water and on sources of noise that interfere with the receiver’s ability to identify and decode the signal. In addition to abiotic and biotic variables that can influence the probability of acoustic transmitter detection, collision of signals from multiple acoustic transmitters arriving at the receiver at nearly the same time may prevent an acoustic transmitter from being decoded or result in an acoustic transmitter that is recorded incorrectly [18]. Numerous variables can affect detection range in a heterogeneous environment, resulting in variable detection ranges and probabilities at a receiver location over time
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