A float-release package for recovering data-loggers from wild sharks

A novel method for determining post-release mortality, behavior, and recovery period using acceleration data loggers

“…Two holes were drilled into the first dorsal fin to allow attachment of a custom-designed data-logger package ( Fig. 1; see Whitmore et al, 2016) containing a G6a ADL (CEFAS Ltd., Lowestoft UK) set to record tri-axial acceleration at 25 Hz, depth at 1 Hz, and temperature at 0.033 Hz, as well as a VHF transmitter (MM180B, Advanced Telemetry Services, Isanti, MN, USA) for package relocation and recovery. The entire tag-float package was approximately 7 × 11 cm in size and weighed 125 g in air (70 g positively buoyant in seawater; <0.5% body mass).…”

“…The galvanic release dissolved in seawater after 1-7 days, releasing the tag package and allowing it to float to the surface for recovery. In an assessment of release timing accuracy, Whitmore et al (2016) found an overall mean variance of 1% in actual GTR release time compared to expected time. Floating tag packages were detected using a hand-held VHF receiver (R45-20C, Advanced Telemetry Systems, USA), and retrieved by vessel (see Lear and Whitney 2016).…”

Bringing data to the surface: recovering data loggers for large sample sizes from marine vertebrates

“…Acceleration data loggers (G6A + , Cefas Technology Limited, UK) were incorporated into float packages alongside a VHF transmitter with a unique transmission frequency (MM120B, Advanced Telemetry Systems, Isanti, MN), as described by Whitmore et al [28]. These float packages measured 12 × 7 × 5 cm and weighed 125 g in air, 70 g positively buoyant in seawater.…”

“…Float packages were attached to the first dorsal fin of sharks using a tether made of plastic zip ties or monofilament with a builtin galvanic timed release (GTR; International Fishing Devices Inc., Northland, New Zealand), which corrodes in seawater after a set number of days depending on the type of GTR ( Fig. 1; also see [28]). Once the GTR corroded, the package released from the shark and floated upright on the surface where the VHF tag could be detected using a handheld VHF receiver (model #R410, Fig.…”

“…The GTR corrodes after a set amount of time and the float package detaches from the fin, floating upright on the surface (b), so that it can be detected and tracked down using a VHF receiver (c) and recovered. See Whitmore et al [28] for additional information on the data logger float package Advanced Telemetry Systems, Inc., Isanti, MN) from a minimum of 10-12 km away. The VHF float packages were set to pop off the sharks 10-72 h after release, while the larger float packages with incorporated satellite tags were set to pop off after 5-7 days.…”