9781934874264-ch5

Telemetry Techniques: A User Guide for Fisheries Research

Section 5.1: Radio Telemetry in Fresh Water: the Basics

Valerian B. Kuechle and Peter J. Kuechle

doi: https://doi.org/10.47886/9781934874264.ch5

Radio telemetry has been used to monitor fish in freshwater since the late 1960s (Lonsdale and Baxter 1968). It followed the earlier use of sonic techniques (Trefethen 1956; Trefethen et al. 1957). Acoustic telemetry was initially used due to the widely held belief that radio waves would be totally attenuated by water. Much of the early research on radio wave propagation in water focused on communicating with submarines in the ocean, and the difficulties encountered undoubtedly contributed to this belief. Due to these disappointing results and the lack of published information on radio wave propagation in freshwater, it took some time for telemetry users to realize the differences between using radio telemetry in highly conductive salt water versus relatively low conductivity freshwater. Since that time, numerous papers on signal behavior in freshwater have been published by both fishery users and the electrical engineering community (Hafez et al. 1979; Lonsdale and Baxter 1968; Shen et al. 1976). Thus, we now have a much clearer understanding of the parameters which determine the success or failure of an aquatic radio telemetry application.

Radio telemetry is used primarily in freshwater, although it has also been applied to marine animals that break the surface of the water. We consider water with conductivity of less than 1000 microSiemens/centimeter (μS/cm) as freshwater. Most freshwater will be below 500 μS cm. In contrast, the conductivity of salt water can be as high as 50 S/cm. In order to develop a system that best addresses the research needs and to use it effectively, it is important to understand all elements that make up an aquatic telemetry system. In this Section we describe those elements and explain how they influence the outcome.

Radio telemetry systems are gear-intensive and dependent on the surrounding environment. The major components of the system include a: