Factors Affecting Reception Range of Ultrasonic Tags in a Georgia Estuary

Abstract

Ultrasonic tags are commonly used for marine biotelemetry, but little or no information exists about the in situ reception range or how different environmental variables affect the reception range of telemetry equipment. In this study, I used active tracking techniques to empirically determine three environmental effects on reception range of ultrasonic tags. Specifically, I examined the effects of (1) tag depth, (2) depth under the hydrophone, and (3) presence of snapping shrimp (Alpheidae) on the reception range of an ultrasonic transmitter (tag) in a Georgia estuary. Placing the tag in deep (8.8‐11.3 m) versus shallow (0.6‐1.5 m) water while the hydrophone was over deep water (3.4‐11.3 m) caused no significant difference in reception range. Placing the hydrophone over shallow (0.6‐2.7 m) versus deep (6.4‐9.1 m) water while the tag was in shallow (1.2‐1.8 m) water caused a significant decrease in reception range. The presence of a large aggregation of snapping shrimp between the hydrophone and the tag also caused a significant decrease in reception range. This study highlights the need for researchers to field-test equipment before conducting telemetry projects.