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

Testing the waters: context-dependence of movement behaviour in marine predators – the bull shark (Carcharhinus leucas) as a model organism  (#54)

Nicolas Lubitz 1 , adam barnett 1 , Marcus Sheaves 1 , Ryan Daly 2
  1. James Cook University, North Ward, QLD, Australia
  2. 2 Oceanographic Research Institute, Durban, South Africa

Mobile marine predators connect habitats and can exert spatially varying predation pressure through seasonal movements. Nonetheless, movement patterns in most taxa are highly variable, with residents and long-distance migrants present in the same population. This complexity has obscured a clear understanding of causes and consequences of individual movement decisions. Here, we apply a context-based approach to study movement drivers of bull sharks by comparing movement patterns of acoustically tagged sharks at the centre of distribution vs. the range limit in Southern Africa. We utilised remote-sensing/in-situ environmental data, tracking of prey species as well as reproductive data on bull sharks. Results show that complex interactions between environmental factors, prey dynamics and reproduction create a distinct distribution of movement strategies along the coast of Southern Africa that may have strong consequences for connectivity and population structure. Additionally, while bull sharks are predicted to expand their distribution poleward in Australia under future climate change scenarios, climate change driven intensification of cold-water upwelling systems at the range limit in Southern Africa is likely to retract their distribution in the future. Overall, this highlights the importance of considering context when making inferences about the impact of global change on mobile predators and resulting habitat connectivity