Struggling with age: Common sawsharks (Pristiophorus cirratus) defy age determination using a range of traditional methods

Populations of sharks are declining globally, largely due to fishing pressure. There is a lack of fisheries-independent data on the demographics of many species, particularly those inhabiting deeper waters. The common sawshark (Pristiophorus cirratus) is a benthic-associated shark endemic to southeastern Australia that has been fished for over 90 years. Despite regular landings, little is known about their lifespan. To assess the age of P. cirratus, we first assessed their vertebral morphology to determine the best method for band pair elucidation. Based on morphology, vertebrae located in the post-branchial region were identified as the largest and least variable for band pair analysis. A total of eight different age-determination methods were then applied to shark vertebrae from this region to test the viability of traditional and nontraditional techniques in elucidating band pairs. Band pairs were indeterminable across all treatments. This research calls for further work into age validation and development of novel techniques to accurately age sawsharks.