An improved technique for small-scale radio-tracking of crayfish and benthic fishes in upland streams

This study measured the accuracy of two radiotracking techniques: (1) triangulation using a Yagi antenna and (2) a form of direct location, the extended-reach technique, which uses a small loop antenna attached to a lightweight 9-m telescopic pole. The study was conducted in the Cotter River, an upland stream in the Australian Capital Territory. Radio tags were positioned instream to determine whether depth, substrate, or local bank profile affected radiotracking accuracy. The extended-reach technique was more accurate (mean error ± SE = 1.00 ± 0.21 m) than triangulation (2.57 ± 0.21 m). Decreased accuracy resulted from the triangulation of radio tags positioned close to boulders or in water more than 1 m deep. These variables had no effect on the accuracy of the extended-reach technique. The presence or absence of a steep rocky bank did not affect the accuracy of either radio-tracking method. The increased accuracy of the extended-reach technique provides an improvement over traditional methods for studying the small-scale movement and microhabitat use of crayfishes (e.g., Eustacus spp.) and benfhic fishes in upland streams.