The critical detection distance for passively tracking tagged fish using a fixed radio telemetry station in a small stream

Abstract

BackgroundFixed radio telemetry stations are used to study the movement ecology of fishes in streams and rivers. A common assumption of such studies is that detection efficiency remains constant through space and time. The objective of this study was to understand how site characteristics and tag distance can influence the detection efficiency of a fixed receiver when used for fisheries research in a small stream. Field tests included a fixed receiver station on Forty Mile Creek, in Banff National Park, AB, Canada that recorded signals from radio tags over specified distances (i.e., 0 m, 27 m, 53 m, 80 m) within the expected detection range from July to October, 2016. Model selection was used to test which parameters may influence detection efficiency.ResultsThe fixed receiver was able to record an average of 89% of transmissions over the study period. Detection efficiency was greater or equal to 0.97 at tag distances of ≤ 53 m. Detection efficiency significantly declined by 36% to a rate of 0.62 for tags placed 80 m from the fixed receiver. Water temperature and water depth also reduced detection efficiency, but only at the critical threshold of 80 m from the tag. Interestingly, turbidity had no influence on detection efficiency in this study.ConclusionsThis study provided insights into the reliability of fixed receiver stations as a passive tracking technique in small streams. The abrupt change in detection efficiency observed in this study presumably occurs in other systems. Identifying critical detection distance thresholds would appear to be a useful strategy for avoiding false-negative results. It is recommended that researchers who conduct radio tracking studies with fixed arrays should consider the deployment of sentinel tags over the study to understand the system performance.