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

• A data-logger release and recovery package was developed for free-living sharks.
• The package had a recovery success of 95.7% across 47 deployments.
• The package had successful deployments on blacktip, bull, nurse, and white sharks.
• Deployment durations ranged from 1–111 h.
• The maximum shark displacement distance was 35 km.

The rapidly expanding use of high-resolution data-loggers to study marine vertebrates presents a wealth of new opportunities for understanding the behavior, physiology, and ecology of these animals in situ. It also presents a number of new logistical challenges, one of the biggest of which is the need to physically recover the tag in order to acquire data, thus, a novel data-logger release and recovery package was designed and tested. This package consisted of a microsphere-resin float, very high frequency (VHF) transmitter, and galvanic timed release (GTR) device which allowed acceleration data logger (ADL) tags to remain on free-living sharks for several days before detaching from the fin. Upon release, tags floated to the surface and were located using a VHF receiver and yagi antenna. This method has been used successfully on blacktip, bull, nurse, and white sharks to produce an overall recovery rate of 95.7% on 47 deployments over periods of 1–111 h and shark displacement distances up to 35 km. This represents a cost-effective method for recovering data-loggers from sharks and large teleosts.