Non-invasive tag design for tracking ocean top predators

V. Pavlov

Thousands of sharks are tagged globally every year. The purposes of tagging include getting information about their abundance, migrations, physiology, behavior, as well as physical characteristics of the environment like temperature and salinity. Currently most of the methods of tag attachment are invasive including surgical implants, dart tags, pop-up archival tags, and fin-mounted telemetry tags. Non-invasive, flexible fin-mounted tag design was developed for the ocean’s top predators. The concept of this novel tag is based on the advanced control of hydrodynamic forces and moments influencing tag attached to the dorsal fin of swimming shark. External tag design generates the resulting hydrodynamic force providing for the robust attachment of tag without utilization of bolts or other invasive methods. This is the first bio-inspired tag design mimicking the natural mobility of dorsal fin to minimize tag impact during active swimming and maneuvering. This feature of tag makes it important in studies of migratory species where the cost of swimming is crucial for the survival. It also makes it advantageous in study of the endangered species, where the invasive methods are prohibited, or subadults with vulnerable energy balance. The tag has improved storage capacity compared with the existing models of the invasive fin-mounted tags. This feature expands the range of tag applications including acoustic telemetry, video-logging, and VHS/satellite tracking. The first prototypes of tag were tested on captive dolphins and tunas. The results of testing indicate good potential of non-invasive tag design for the telemetry of ocean top predators having dorsal fin, including sharks, dolphins, and tunas.