Acceleration data loggers, iTags: a tool to determine post-release mortality and behaviour of deepwater sharks

Caterina Bosio

Deepwater sharks are highly susceptible to overexploitation due to their very conservative life-history characteristics. Information about their ecology and behaviour is largely unknown, generating difficulties in conservation planning. New tools are necessary to assess the mortality events and define the post-release behaviour of deepwater sharks, that are caught as bycatch. The objective of this study was to evaluate the use of iTags, bio-logging devices provided with inertial measurement units—particularly accelerometers, magnetometers, gyroscopes and pressure sensors— to study the mortality rates and the swimming behaviour of deepwater shark species after their release from fishing boats. The results proved that iTags are resistant to harsh ecosystem conditions such as high pressures and low temperatures. It was also proven that iTags are useful tools to determine fine-scale behavioural data of deepwater sharks after release and to detect mortality events. The study provides a first methodological basis to assess the impact of fishing on deepwater shark species, contributing to their conservation.