Multi-sensor tagging and acoustic analysis for assessment of impact of seismic sparker surveys on leatherback turtle behavior at a nearshore foraging ground

High-resolution geophysical surveys are used in offshore wind development to provide data on seafloor composition. Many of these surveys use seismic sparkers, impulsive acoustic sound sources that generate signals to penetrate the seafloor. As the number of offshore wind projects grows, the impact of sparkers on marine wildlife has become a concern as the broadband sound overlaps with marine wildlife hearing. One approach to assess impact is to deploy animal-borne, multi-sensor tags to track the movement and behavior of animals in response to sparkers. A novel multi-sensor tag was built that included a camera along with an AcSense-Mini, a 1-channel acoustic recorder with IMU, pressure and temperature sensors. The tag was deployed on leatherback turtles in the vicinity of a ship-towed sparker during the fall of 2023. Data from the turtle-borne tags were analyzed for behavioral responses to the sparker; a key part of the analysis was the navigational reconstruction of the turtle track using frequency-dependent sound pressure levels with the IMU data. Findings include the acoustic sound source characteristics, two case studies of turtle response to the closest point of approach to the sparker, and limitations on turtle trajectory reconstruction to inform future design [Work funded by Bureau of Ocean Energy Management.]