Temperature utilization in a coral reef flat specialist, the epaulette shark, Hemiscyllium occelatum

Ms Tiffany  Nay1,2, Mr Rohan Longbottom2, Mr Connor Gervais3, Dr Jodie Rummer1,2, Dr. Jacob  Johansen4, Dr. John  Steffensen5, Dr Andrew Hoey1,2

1James Cook University, Townsville, Australia, 2ARC Center of Excellence for Coral Reef Studies, Townsville, Australia, 3Macquarie University, Sydney , Australia, 4University of Hawaii, Kaneohe, United States of America, 5University of Copenhagen, Helsingør, Denmark

Intertidal and shallow, subtidal habitats present some of the most challenging environmental conditions for resident species. For example, coral reef flats can experience temperatures that are 3-4°C warmer than surrounding habitats on a daily basis and seasonal temperatures spanning a 12°C range. Species occupying these habitats may use behavioural and/or physiological strategies to cope with the extreme and variable conditions. We investigated the potential for a common reef flat inhabitant, the epaulette shark, Hemiscyllium ocellatum, to use movement (i.e., move to more thermally favourable microhabitats) as a strategy to maintain optimal body temperatures. Firstly we determined the preferred temp of sharks under controlled conditions using an automated shuttlebox. We then compared the preferred temp to both the available temps across the reef flat and the internal body temp of tagged individuals on the reef flat of Heron Island. While sharks in the lab showed a clear preference for 20.5C, irrespective of gender or season, we found no evidence for sharks moving to realise this temperature in the wild. That is, internal body temperature of wild sharks mirrored external environmental conditions. Elasmobranch species are generally thought to rely on movement to select thermally beneficial areas or evade suboptimal conditions; however, we suggest species like the epaulette shark may instead rely on other strategies in response to temperature changes. For meso-predators, like the epaulette shark, determining how rising temperatures will affect physiological performance and distribution patterns will be key in understanding how ocean warming will affect coral reef ecosystems into the future.


Biography:

Connor Gervais from Macquarie University, Sydney Australia. I primarily study the strategies fish utilize in response to environmental stressors, with a particular focus on the development of elasmobranchs. Specifically I am interested in how temperature may impacts their physiology and behaviour during these early life stages. While, focused on specific species traits, I really want to understand how these traits may affect species in the wild, with a greater context as to their response(s) to climatic changes in their habitat and the knock-down effects across their life-history.

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