Movement, vertebral morphology and age dynamics of the common sawshark Pristiophorus cirratus

The common sawshark (Pristiophorus cirratus) is a deepsea shark endemic to southeastern Australia that has been fished for over 90 years. We explored two critical parameters required for effective fisheries management: movement ecology and longevity. To investigate movement ecology, three common sawsharks were tagged with passive satellite archival tags (PSATs) off the northeast coast of Tasmania in 2016. Archived data suggest sawsharks are able to move larger distances than previously thought and engage in vertical movements with a diel pattern observed. To gain insight into the longevity of sawsharks, we first assessed their vertebral morphology to best direct age determination efforts for vertebral band pair analysis. Vertebrae located in the post-branchial region were found to be the largest and least variable throughout ontogeny and therefore most ideal for band pair analysis. A range of age determination methodologies, traditional and non-traditional, were then applied to shark vertebrae to test the efficacy of vertebral band-pair analysis in sawsharks. Bands were indeterminable across all methodologies. This study provides insights into population dynamics and vertebral morphometrics and offers direction for future age determination studies in sawsharks. Such information will provide vital information for the conservation and management of this data-poor species.