Investigating how seasonal changes alter wild juvenile Atlantic Salmon (Salmo salar) environmental DNA quantification in New Brunswick, Canada

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University of New Brunswick


Environmental DNA (eDNA) analysis is valuable to monitor imperilled taxa; however, unexplained observed eDNA variation impedes the development of population abundance models. To address unknown seasonal impacts on the quantitative relationship between eDNA concentration and abundance, I studied seasonal eDNA dynamics of Atlantic Salmon (Salmo salar) along 9 km of a river in New Brunswick, Canada. During spring smolt emigration, I tested the eDNA-abundance relationship and the relevance of environmental factors in population models. Environmental variables were also tested in summer with relatively constant parr abundance at two different spatial scales. Environmental covariates significantly altered eDNA concentration in both periods and their inclusion within eDNA models was crucial to assess smolt and parr populations. This study discusses mechanisms behind the seasonal effect of a local environment on eDNA and provides recommendations to develop salmon eDNA monitoring programs using empirical-based evidence of the relative importance of environmental interactions.