Standard Talk (15 mins) Australian Society for Fish Biology Conference 2022

Consistent circadian rhythms across populations and life stages of a globally-distributed marine predator (#96)

Oliver Jewell 1 , Taylor K Chapple 1 , Salvador J Jorgensen 1 , Charlie Huveneers 1 , Megan Winton 1 , Gregory Skomal 1 , Paul Kanive 1 , Jerry H Moxley 1 , Scot Anderson 1 , David Edwardson 1 , Barbara A Block 1 , Nicola Armstrong 1 , Nicholas Payne 1 , Jayson Semmens 1 , Yuuki Y Wantanabe 1 , Adrian C Gleiss 1
  1. School of Biological Sciences, University of Western Australia, Perth, WA

Circadian rhythms are innate responses to cyclic daily changes in the environment (e.g. night and day) allowing physiological and behavioural processes such as feeding or resting to occur at the most suitable times. Given that circadian rhythms are thought to be an adaptive response to prevailing conditions, it raises the question of whether globally-distributed species display adaptative routines in response to local conditions. Here, we tested if the circadian rhythm of the white shark, Carcharodon carcharias, a circumglobally-distributed marine predator, differs among four populations and across eight aggregation sites in three of the world’s oceans. We derived the diel activity of 104 sharks through motion-sensitive biologgers that collected over 2,500 hours of activity data. Overall, we found that diurnal circadian rhythm was conserved across all populations but found site-specific differences in this diurnality, with the activity of some populations peaking before noon, while others peaked in the afternoon. Our results suggest that despite diverging thousands of years ago, the circadian rhythm of white sharks has largely remained consistent with only minor local adaptation. We suggest that maintenance of this diurnality is a result of sensory specialisation, while the minor variations of the timing of activity is an adaptive response to the availability of prey.