Bioenergetic Responses of Coldwater Fishes to Thermal Regimes and Productivity in Western Lakes and Reservoirs: Opportunities and Constraints for Conservation

Temperature, food availability, and predation risk form vertical gradients determining growth and survival for fish in lakes and reservoirs. These gradients change on inter-annual, seasonal, and diel temporal scales and are strongly influenced by climatic variability, conflicting water demands and management. Temperatures associated with optimal growth and energy loss vary both among life stages and species, but the quantity, quality, and spatial distribution of available food resources can significantly alter these thermal responses. By combining data or projections of thermal stratification regimes with the vertical distribution of prey and bioenergetic capabilities of species and life stages of fish, we can formulate predictions about spatial-temporal overlap among prey, competitors and predators. When overlaid on life history requirements, we can identify potential bottlenecks to growth or survival and evaluate responses to climatic variability, water management, or new species. Greater understanding of how climatic variation and water management affects the timing, magnitude, and duration of thermal stratification, and how key species and their supporting aquatic resources respond can improve projections of and strategies for managing aquatic resources under future climatic conditions.  This knowledge can also inform future development and operation of water storage facilities within the context of localized environmental and ecological constraints.