UC Davis

Bioenergetics is the study of how energy flows through and transforms within organisms. Variables such as temperature and food availability have variable effects on growth and metabolism. There is an increasing interest in determining fish bioenergetics in conjunction with behavior and life-history traits to predict species-specific responses to climate change.The Sacramento-San Joaquin River Basin, California, USA, supports multiple species of anadromous fishes – Chinook salmon, green sturgeon, and white sturgeon – which return to these freshwater natal habitats to spawn. Many of the physical and ecological characteristics of this watershed have been impacted by physical modifications and climate change. Specifically, dams and channelization have led to changes in water temperature, flow, and altered food web dynamics. Early life stages of fish are particularly vulnerable, and declining recruitment is thought to contribute to precipitous population decline. Each chapter addresses an aspect of fish bioenergetics, using metabolism as a foundation due to its representation of the sum of biochemical processes used for energy intake and support for life functions. Chapter 2 examined the metabolic cost of digestion in juvenile Chinook salmon across a broad range of temperatures, finding that the digestive response largely retains its energy efficiency at all temperatures. Chapter 3 determined the scaling of metabolic rate and differences in developmental trajectories across early ontogeny of green sturgeon, finding that rearing in suboptimal cold temperature is metabolically costly and leads to large size-at-age delays. Chapter 4 investigated the relationship between metabolic rate and locomotory activity in juvenile white sturgeon under nutritional stress, finding that the relationship is context dependent, requiring sufficient exposure to nutritional stress. Collectively, my research investigated stage- and species-specific aspects of larval and juvenile fish bioenergetics that can help us understand how various environmental stressors may impact fish populations. The intersection of bioenergetics, behavior, and organismal performance is critical for continued insight on species- and ecosystem-wide responses to perturbations, because it illuminates the diversity of physiological and behavioral responses available to fish. By investigating these responses with respect to current and expected climate-induced conditions, we can better craft management strategies to conserve these commercially and culturally important native California fishes.