The physiology of social and environmental stress in fish

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The long-term objective of my research program is to understand the physiology of stress in fish. Fish (and other animals) regularly face physical and/or biological factors that threaten their homeostasis. In response to such stressors, a co-ordinated suite of behavioural, neuroendocrine, and cellular events is initiated to enable the animal to overcome the threat. Despite the importance of stress responses to the health/survival of individuals and populations, our knowledge of how they are regulated and integrated with other physiological systems remains limited, particularly during chronic stress. The proposed research will use chronic social stress as a system in which to study regulation of the stress axis. Juvenile salmonid fish establish social hierarchies in which individuals of higher rank profit (e.g. grow better) at the expense of lower-ranking fish. We will study the regulation of metabolism in the liver of subordinate fish to understand how it is affected by chronic stress and how this, in turn, affects fish growth. We also will try to understand how and why circulating cortisol (stress hormone) levels in subordinate fish are persistently elevated but at the same time, subordinate fish are unable to further elevate cortisol in response to an additional, acute stressor. Finally, we will explore the possibility that maternal stress affects offspring stress responses - this is well-established for mammals but has received little attention in fish. To complement our work on social stress, we will examine an environmental stressor by characterizing the role of cortisol in regulating acid-base responses. Collectively, the proposed research will advance our fundamental knowledge of the physiology of stress in fish. Fish can be subjected to multiple stressors both in the natural environment (e.g. angling, toxicants, climate change, acid water plus predation, social interactions, changes in water flow) and in aquaculture settings (e.g. high holding density, handling). Understanding how they respond to these multiple stressors is key to better managing both wild and aquaculture populations.