Energy Metabolism and Nutritional Condition of Juvenile White Sharks (Carcharodon carcharias; Linnaeus, 1978)

Examining the relationship between an animal’s diet and physiology is crucial to understanding their responses to environmental change. Dietary-induced physiological variation can influence key life history processes, including growth and reproduction, ultimately affecting individual fitness. Reported here are the plasma biochemical parameters related to energy storage, use and nutritional condition in juvenile white sharks (Carcharodon carcharias) in Eastern Australia. Specifically, we used plasma metabolites (triglyceride, cholesterol and β-hydroxybutyrate), thyroid hormone thyroxine and fatty acid profiles from 50 juvenile white sharks (152–340 cm total length) captured on SMART drumlines in Eastern Australia to examine blood biochemistry and nutritional ecology. Concentrations of triglycerides and β-hydroxybutyrate indicated high energy expenditure likely associated with the broad-scale migration of white sharks along the Australian coast, highlighting the importance of β-hydroxybutyrate as an energy source. Seasonal variation in the triglyceride/cholesterol and ω3/ω6 fatty acid ratio, in conjunction with lower docosahexaenoic acid, suggests that lower-quality prey is consumed during winter months, thereby influencing the nutritional condition of these sharks. Additionally, the positive correlation between thyroxine concentrations and water temperature suggests reduced metabolic activity during cooler months. Such fluxes in food quality and nutritional condition may affect juvenile white sharks’ growth and development rate and future reproductive success.