Abstract: Myriad anthropogenic impacts drive declines in global shark populations; yet, the extent that global climate change threatens sharks is poorly understood. Recent experimental evidence demonstrates behavioural and physiological responses of cold-water species to simulated ocean warming (i.e., elevated temperature) and acidification (i.e., elevated CO₂) conditions. However, previously studied species occupy a narrow ecological niche such that predicted responses to projected climate change conditions are not representative of most other groups, including tropical species. This thesis tested the hypothesis that predicted climate change stressors (ocean warming and acidification) affect aspects of the physiology and behaviour of reef shark neonates using the blacktip reef shark (Carcharhinus melanopterus) and sicklefin lemon shark (Negaprion acutidens) as experimental models. Specific objectives were to define 1) thermal dependence of growth, metabolic rate, and abundance of seasonally acclimatised neonates in situ, 2) stress responses and oxygen uptake rates (proxies for metabolic rate and whole-organism performance) of neonates in situ, 3) thermal dependence of oxygen uptake rates, growth, and environmental tolerance traits in thermally acclimated neonates ex situ, and 4) physiological and behavioural responses of reef shark neonates acclimated to combined temperature and CO₂ conditions. The findings of this thesis suggest that these populations of reef shark neonates will not be resilient to the combined effects of ocean warming and acidification. These data are, therefore, applicable to conservation planning for these and similar reef shark populations by identifying tolerance thresholds to environmental change at a critical life-history stage.

Biography: Ian is a cotutelle PhD candidate at the Australian Research Council Centre of Excellence (ARC CoE) for Coral Reef Studies and École Pratique des Hautes Études (EPHE). Previously, Ian completed his B.Sc. in ecology and evolutionary biology at the University of Michigan, and his M.Sc. in natural resources and environmental sciences at the University of Illinois. Ian’s research interests are in fish ecophysiology and conservation physiology, with a focus on elasmobranch fishes. Prior to pursuing a PhD, Ian’s research aimed to understand the energetic costs, physiological stress, and behavioural responses of sharks to longline capture, including the implementation of bycatch reduction devices. In October 2016, Ian started his PhD in Moorea, French Polynesia under the supervision of Associate Professor Jodie Rummer (ARC CoE for Coral Reef Studies), Professor Colin Simpfendorfer (James Cook University), and Professor Serge Planes (EPHE). Ian’s thesis aims to characterise physiological and behavioural effects of climate change related stressors in tropical reef shark neonates.