Explaining variation in stream fish productivity with biotic and abiotic variables across wadeable rivers in eastern North America

Abstract

Abstract Biomass production is a key ecosystem process that provides insight into ecological processes such as growth, reproduction, mortality, and energy distribution. Previous studies have considered various fish response measures such as species richness, abundance, and/or biomass as response variables for river ecosystems or the productivity of particular species. However, few studies have investigated how total fish productivity of riverine systems is affected by environmental variables. Here, we identified important abiotic and biotic predictors of fish productivity in wadeable, temperate riverine systems. We investigated the relationships between total stream fish productivity and multiple abiotic and biotic variables in wadeable stream reaches across Ontario, Canada. Variance partitioning was used to evaluate the relative importance of the biotic, landscape, climatic, and geologic variables on total stream fish productivity. A modified bootstrap approach was used for the model‐selection process and to parameterise an empirical fish productivity model. We found that biotic predictors explained more variation in productivity relative to the abiotic variables. The best empirical model included day‐of‐year, growing degree days, latitude, salmonid presence/absence, species richness, and upstream catchment area. Our findings indicate that a combination of both biotic and abiotic variables can provide valuable insight into how ecological processes, such as fish productivity, differ across ecosystems. Species richness and differences in assemblage characteristics may be key determinants of the overall fish productivity in stream systems. Our model can estimate productivity from salmonid presence/absence data and total species richness, instead of fish abundance data, which require larger sampling efforts.