Field testing a novel high residence positioning system for monitoring the fine-scale movements of aquatic organisms

Abstract

Acoustic telemetry is an important tool for studying the behaviour of aquatic organisms in the wild. VEMCO high residence (HR) tags and receivers are a recent introduction in the field of acoustic telemetry and can be paired with existing algorithms (e.g. VEMCO positioning system [VPS]) to obtain high-resolution two-dimensional positioning data. Here, we present results of the first documented field test of a VPS composed of HR receivers (hereafter, HR-VPS). We performed a series of stationary and moving trials with HR tags (mean HR transmission period = 1.5 s) to evaluate the precision, accuracy and temporal capabilities of this positioning technology. In addition, we present a sample of data obtained for five European perch Perca fluviatilis implanted with HR tags (mean HR transmission period = 4 s) to illustrate how this technology can estimate the fine-scale behaviour of aquatic animals. Accuracy and precision estimates (median [5th–95th percentile]) of HR-VPS positions for all stationary trials were 5.6 m (4.2–10.8 m) and 0.1 m (0.02–0.07 m), respectively, and depended on the location of tags within the receiver array. In moving tests, tracks generated by HR-VPS closely mimicked those produced by a handheld GPS held over the tag, but these differed in location by an average of ≈9 m. We found that estimates of animal speed and distance travelled for perch declined when positional data for acoustically tagged perch were thinned to mimic longer transmission periods. These data also revealed a trade-off between capturing real nonlinear animal movements and the inclusion of positioning error. Our results suggested that HR-VPS can provide more representative estimates of movement metrics and offer an advancement for studying fine-scale movements of aquatic organisms, but high-precision survey techniques may be needed to test these systems.