Monitoring Atlantic salmon (Salmo salar) smolt migration in a large river system using environmental DNA

Effective monitoring strategies are key for aquatic species conservation, but traditional methods often require significant resources, especially in large aquatic systems. The emergence of quantitative environmental DNA (eDNA) is a promising alternative. Yet, few studies have evaluated the possibility of quantifying Atlantic salmon abundance with eDNA when individuals are at low abundance and occur in large river systems. In this study, we tested the efficacy of eDNA to monitor and quantify daily variation in smolts counts during their downstream migration in a large river system with low abundance of smolts. During the 2021 and 2022 downstream migrations, trap nets were used to conduct a daily census of smolts in the Romaine and Puyjalon rivers (Québec, Canada) while eDNA samples were collected daily over a transect perpendicular to the riverbank. Using quantitative real-time qPCR, we showed that discharge-corrected eDNA concentrations were positively correlated with daily smolt counts..., , # Monitoring Atlantic salmon (Salmo salar) smolt migration in a large river system using environmental DNA

Dataset DOI: [10.5061/dryad.mw6m9067j](10.5061/dryad.mw6m9067j)

## Description of the data and file structure

We provide here the complete data set we used in our article : Monitoring Atlantic Salmon (*Salmo salar*) Smolt Migration in a Large River System Using Environmental DNA.

You will find three sheets in the excel. The first one describe all variable present in the study along with their unit and transformation. Second sheet is the dataset we used to predict capture with eDNA modified concentration. Finally, the third one is the complete capture of smolts before, during and after eDNA sampling used for Figure 2 in the article.
### Files and variables

#### File: modelling\_data.xlsx

**Description:** Data used for the study. Variables are describe below with unit in bracket.

##### Variables

| Variable | Unit | Description ...,