The Fitzroy River in the Kimberley region of Western Australia represents one of the last intact nursery habitats for the critically endangered freshwater sawfish (Pristis pristis). However, this region is under increasing threats from both climate change and land use actions, which include proposals for significant water extraction to fuel agricultural development. Both of these factors have the potential to substantially change the physical characteristics of this crucial nursery habitat, including river flow rates and water temperatures. Understanding how sawfish will respond to these changing environmental variables is thus crucial to informing conservation measures for these animals and their unique ecosystem. Here we use a combination of respirometry and accelerometry methods to decipher patterns of behaviour and energy use in free-ranging sawfish. Field energy expenditure, activity levels, and body condition are compared between multiple years within 2011-2017 characterized by significant wet seasons and resulting high water levels, flow rates, and generally lower temperatures, and by poor wet seasons, low flow rates, and higher water temperatures. Results are discussed in the context of forecasting how sawfish may respond to climate change and land development in the Fitzroy region, and informing management and conservation measures for this critically endangered species.