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

First insight into the fine-scale swimming and diving behaviour of the southern eagle ray (Myliobatis tenuicaudatus) (#18)

Lachlan George 1 , David Moreno 1 , Sean Tracey 1 , Yuuki Watanabe 2 , Jayson Semmens 1
  1. Fisheries and Aquaculture, Institute for Marine and Antarctic Studies, University of Tasmania, Taroona, TAS, Australia
  2. National Institute of Polar Research, Tokyo, Japan

Advances in biologging technology have enabled researchers to monitor the fine-scale movements and behaviour of numerous elasmobranchs (sharks, skates and rays), improving our understanding of how these animals behave and the biomechanics associated with specific behaviours. With this said, there is very little information detailing the fine-scale behaviour of Batoids through the use of biologgers. In this study, we attached a multi-sensor biologging package to southern eagle rays (Myliobatis tenuicaudatus) in southeast Tasmania to investigate their fine-scale swimming and diving behaviour. A total of 12 eagle rays (892 ± 141 mm; mean and ± SD) were successfully tagged with a biologging package in 2014 (n=4) and 2020 (n=8), recording over 952 h of triaxial acceleration, depth and temperature data and >7 h of video footage. When not stationary on the benthos, eagle rays oscillated through the water column similar to pelagic sharks, descending and ascending at relatively shallow angles (-5.53 ± 4.45° and 9.42 ± 6.33° respectively) and occasionally making dives to depths >38 m. Gliding behaviour (the cessation of wingbeats) was also observed during the descent phase of most dives. This oscillating behaviour is likely a combination of searching for prey and/or predator avoidance, and an energy efficient mode of transport that utilises gliding during descent to reduce the cost of locomotion. This study is the first to describe the swimming and diving behaviour of the southern eagle ray, highlighting that this species is not confined to the benthos and regularly makes vertical oscillations through the water column.