Fish display a wide range of life history strategies, for which resources must be allocated delicately, providing the perfect opportunity to investigate the effects of extrinsic and intrinsic factors on oxidative stress. In Chapter 2, I found that oxidative ecology in fish is largely understudied. In Chapter 3, I demonstrated that cortisol caused an increase in glutathione in the short-term, and that oxidative stress levels as well as low molecular weight antioxidants decreased in the short-term in all treatments. Interestingly, I show that overwinter survival may be associated with low total glutathione and low oxidative stress levels. In Chapter 4, I demonstrated that migratory individuals have a higher antioxidant capacity than their resident counterparts. Continuing studies on the oxidative ecology of fish may help to uncover the physiological mechanisms that influence behavior in relation to ecological phenomena.