Towed-float GPS telemetry: A tool to assess movement patterns and habitat use of juvenile stingrays

Abstract

GPS telemetry provides high-accuracy spatial data on animal movement; however, it has rarely been used with benthic organisms, such as stingrays, because of their irregular surfacing behaviour or bottom-dwelling habits. This study evaluated the use of towed-float GPS tags to assess movements of juvenile stingrays, with active tracking performed simultaneously for comparison. Four juvenile Urogymnus granulatus individuals (2 females and 2 males; average 32.2-cm disc width) were tracked in April 2016. Individuals travelled 1332.15 ± 269.58 m south-east across Pioneer Bay at an average speed of 6.87 m min-1 in 3.7 h. Stationary tests demonstrated that the quality of the data obtained by towed-float GPS tags could not be matched by active, acoustic or ARGOS telemetry, reaching, on average, 99% of successful fixes and <15-m accuracy. Location error varied significantly based on the number of satellites detected, with error decreasing as the satellite number increased. This study demonstrated the potential of towed-float GPS telemetry for high-resolution assessment of movement patterns and habitat use of juvenile stingrays in shallow coastal water. If well applied, this technique can increase our knowledge of juvenile stingray ecology and their essential habitats.