Relationship between brook charr ( Salvelinus fontinalis ) eDNA concentration and angling data in structured wildlife areas

Abstract Accurate management of exploited fish populations is essential to ensure their long‐term sustainability. The use of eDNA as a tool for providing information on population relative abundance offers much potential although few examples in a fishery context have been documented. In this study, we collected 600 water samples from 30 lakes in Québec (Canada) to document the relationship between brook charr (Salvelinus fontinalis) angling data and their lake's eDNA concentration. Model selection with angling data and environmental parameters was used to find the best predictive model for eDNA concentration. We found a strong correlation between the average fish density from current and previous years (fish harvested/ha, adj. R2 = 0.76) with the mean eDNA concentration among lakes, supporting the growing trends in the literature. We observed very similar levels of correlation either when eDNA and angling data were from the same year or different years. We also found a pronounced inter‐year difference in lakes' eDNA quantity measured in 2019 and 2020. We hypothesize that the main drivers for this difference were inter‐seasonal variation including water temperature and associated variation in fish behavior. These results support the usefulness of eDNA as a quantitative tool for exploited fish populations.