Variability of fish production : nutrients as chemical drivers across a diverse geographic range

Abstract

Total phosphorus (TP) is an essential nutrient established as a driver of primary productivity that we predict plays a large role in the fish biomass in rivers, lakes and reservoirs. Watershed catchment geology and anthropogenic modification to river flow including hydropower influence nutrient variability in rivers. The relationship between nutrient variation and fish biomass was compared on a local-scale between two geological distinct mountain watersheds in southeastern BC, providing an opportunity to examine smaller-scale ecosystem response to nutrient availability. Nutrient regimes were also characterised in rivers regulated by hydropower and reference rivers across Canada to assess water quality trends and expected variability in fish biomass across a broad geographic scale. Local scale aquatic assessment is useful for identifying trends in ecosystem response within a watershed, whereas regional assessments are at a scale that is more applicable for management. Using TP and fish biomass relationships from a meta-analysis of literature, we developed regionally specific nutrient-based fish models. Establishing baseline nutrient regimes and developing models to estimate expected fish biomass specific to regional fish diversity, provides a useful predictive tool for initiating mitigation and compensation for rivers affected by hydropower.