It is imperative that we understand the physiological, behavioural and ecological consequences of stress in wild animals. This thesis presents an integrative and multidisciplinary study on the ecology of stress in a tropical coastal marine fish, the checkered pufferfish (Sphoeroides testudineus). By incorporating physiological and behavioural tools, I quantified individual variation in the glucocorticoid (GC) stress response and established a negative relationship between the GC stress response and two established fitness proxies of the pufferfish (chapter 2). GCs were then experimentally
elevated for the purpose of investigating the thermal-related consequences on the pufferfish in the laboratory and in their natural coastal habitat (chapter 3). Various consequences were documented including fluctuating GCs and weakened fitness proxies to thermal shock, and minor variations in ecosystem dynamics. As a whole, this thesis improves our understanding of the ecology of stress in a wild tropical fish population.