Section 5.3: Tracking Aquatic Animals with Radio Telemetry
John H. Eiler
Previous Sections have discussed aspects related to conducting a telemetry study, including the technical attributes of the transmitters and receiving equipment, overall study design, and tagging methods that minimize adverse impacts on the animals being studied. In addition to these considerations, an essential requirement of any successful project is the ability to effectively relocate the individuals that have been tagged.
A variety of aquatic fauna (hereafter referred to as fish, although our discussion also applies to other animals) have been tracked using radio telemetry since the early 1960s, although the methods used have evolved substantially. Initially studies were limited to small numbers of individuals (usually <40) in confined areas. Technological advances have made it possible to track large numbers of fish, wide-ranging species, and smaller individuals. Telemetry is increasingly being used to obtain quantitative as well as qualitative information ranging from fish movements, distribution, and habitat use (Eiler et al. 1992; Hilderbrand and Kershner 2000; Zigler et al. 2003; McCleave et al. 2006) to physiology and bioenergetics (Hinch and Rand 1998; Cooke et al. 2006; Weatherley et al. 2006). Tracking methods can be relatively straightforward when dealing with a few localized individuals, but monitoring large numbers of fish over vast expanses can be extremely challenging. Although the methods used can have a major impact on study success, the technical details used to address these challenges are often not included in published accounts.
This Section discusses the technical aspects and practical considerations associated with tracking fish. Understanding the technical capabilities and limitations is essential for selecting methods that are effective and provide usable information. Methods suitable for determining habitat use in small, urban streams will differ substantially from those used to study migratory patterns over substantial distances. Although this Section focuses primarily on tracking methods used in rivers, these techniques also applied to lacustrine environments. Tracking fish in lakes occasionally requires special considerations, which are discussed separately (Section 6.4). Many of the examples used in this Section are from telemetry studies on adult salmon (Oncorhynchus spp.) in Alaska. Although the research objectives, scale, life stage, and field conditions encountered in other studies may differ, the underlying principles are applicable to the problems faced by most researchers.