Section 7.2: Detection Efficiency in Telemetry Studies: Definitions and Evaluation Methods
Michael C. Melnychuk
Acoustic and radio telemetry are valuable tools for studying the movements and dynamics of animal populations. Some studies combine telemetry methods with mark–recapture or tag-recovery modeling to estimate population abundance or demographic rates such as survival, individual growth, recruitment, and transition among habitats (reviewed in Pine et al. 2003). Other studies use telemetry techniques for assessing movement patterns as they relate to habitat use, foraging behavior, or interactions with other species. Many kinds of biological questions can be posed, and answering them often involves estimating how many tagged animals are still alive and/or still present in an area at some time.
Since some tagged animals may not be detected during the sampling process, estimates of numbers alive and biological rates (survival, movement) are confounded and therefore depend on the probability of transmitter (hereafter referred to as tag) detection. This detection probability (or equivalently, detection efficiency, DE) nuisance parameter must be estimated to obtain unbiased estimates of the survival or movement parameters of interest. Despite the widespread and increasing use of telemetry, there has generally been a paucity of studies that evaluate different methods for estimating DE (Clements et al. 2005).
Biological hypotheses and study objectives should drive the design of telemetry arrays and sampling methods (Heupel et al. 2006). Similarly, the meaning of DE and methods to quantify it also differ depending on study objectives. This Section is written to present the diverse usage of “detection efficiency” in telemetry studies and to describe the variety of evaluation methods available. Several environmental and technological factors which can affect DE are also outlined. The text generally refers to fish, but the ideas are transferable to telemetry studies involving other aquatic taxa and/or terrestrial animals. Examples given in this Section generally involve acoustic tracking studies, but the definitions, topics, and methods presented have application to radio telemetry as well.