Metabolic life tables: the sockeye salmon example

We resurrect the metabolic life table (MLT), a combination of life table and energy budget that quantifies how metabolic energy is acquired and allocated to survival, growth and reproduction over the life cycle. To highlight its broad implications and utility, we apply this framework to John Bretts classic data on sockeye salmon. In the life cycle of Skeena River sockeye, a pair of breeders dies in fresh water after spawning, and the offspring move to the ocean where they feed, grow and suffer mortality before returning to freshwater and migrating upstream to spawn and die. Most of the accumulated biomass energy is transported into freshwater ecosystems and expended on respiration for migration and breeding or is transferred to consumers. Reanalyzing Bretts data in the context of a MLT has broad implications and applications: i) for basic ecology, because of the unusual physiology, life history and ecosystem impacts of wild salmon; and ii) for conservation and management, because of the enormous economic importance of wild-caught and farmed salmon. Moreover, the MLT highlights the intimate relationships between two universal biological processes: i) demography as a function of age; and ii) metabolism, the balancing of uptake, transformation, and allocation of metabolic energy over the life cycle. Linking these two universal processes provides a general MLT framework that can be applied across the diversity of life.