The role of Atlantic salmon (Salmo salar) in ecological restoration: Insights from four Atlantic Canadian National Parks

Abstract

Atlantic salmon play a critical role in maintaining healthy river ecosystems. With declining populations, the ensuing magnitude of change in freshwater production is unknown, largely due to a lack of baseline characterization of riverine ecosystem function. Across seven rivers in four Canadian National Parks, our study explores how freshwater production and function vary along a gradient of Atlantic salmon populations (i.e. gradient of marine derived nutrient (MDN) inputs). We evaluate the spatio-temporal influence of ongoing salmon restoration on (1) riverine benthic production through biofilm community response and (2) use stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) to characterize MDN uptake in community isotopic structure, specifically examining MDN assimilation in juvenile salmonids. Results suggest a marked increase in benthic production and MDN uptake into freshwater food webs when spawning Atlantic salmon are present in ecologically relevant numbers, allowing managers to more accurately measure and adaptively manage ecological restoration initiatives.