Scuba Diving Tourism Impacts and Environmental Influences on the Patrolling Behavior of Grey Nurse Sharks (Carcharias taurus): A Preliminary Assessment Using Acoustic Telemetry at Fish Rock, Australia

Abstract

The patrolling behavior of the critically endangered grey nurse shark (Carcharias taurus) comprising the occupation of, and movements between, two locations at Fish Rock (off eastern Australia) was documented using passive acoustic telemetry. Sharks occupied the locations symmetrically, asymmetrically, randomly, and nonrandomly. Passive acoustic telemetry was also used to provide a preliminary assessment of the impacts of scuba diving tourism on patrolling behavior. Maintaining natural behaviors unaffected by anthropogenic disturbances including scuba diving tourism is essential for the recovery and long-term conservation of this critically endangered species. The patrolling behavior of replicate sharks on any given day was similar but varied subtly and sometimes markedly in the periods before, during, and after scuba diving typically occurs. In contrast, patrolling behavior varied substantially among days with and without scuba diving; however, this was not statistically significant. Scuba diving did not impact the occupation of, or movements between, the locations by grey nurse sharks. Instead it is likely that the sharks responded to oceanographic features, localized currents, and prevailing sea conditions by adopting a range of swimming behaviors to conserve energy, and this accounted for the variation in patrolling behavior among days. Future research at other aggregation sites, during different lunar phases and with sharks at various life history stages should be done to confirm the findings of this first assessment and to enhance the generality of the results to grey nurse sharks elsewhere. Regular monitoring of grey nurse shark scuba diving tourism should be done to ensure that any anthropogenic disturbances are identified so that mitigation can be implemented.