An assessment of juvenile sand tiger (Carcharias taurus) activity patterns in a seasonal nursery using accelerometer transmitters

Abstract

Telemetry transmitters incorporating accelerometers have recently emerged as powerful tools for investigating the activity patterns of individuals and groups of individuals in nearshore environments. Data obtained from these devices provide not only a time series of animal occurrence at acoustic receivers, but also a direct measure of animal activity, which can be used to quantify trends in activity states over time and in relation to exogenous factors. Here we used passive acoustic accelerometry to examine trends in the activity and swimming depth of eight juvenile sand tigers (Carcharias taurus) in Plymouth, Kingston, Duxbury (PKD) Bay, Massachusetts, USA, a recently identified nursery area. We applied a novel geostatistical modeling approach that accounts for both latent spatial and individual variation to assess the effects of time of day, tidal stage, water temperature, and lunar phase on activity patterns at both a population- and individual-level. The best-fitting model indicated that juvenile sand tigers were more active and more likely to be detected at the surface at night and during the new moon; water temperature was also a predictor of surface activity. Collectively, our results confirm conventional wisdom that sand tigers are slow-moving fish that are more active at night and provide evidence that high activity in PKD Bay may be indicative of foraging activity.