Understanding Environmental DNA Detection Probabilities: A Case Study Using a Stream-Dwelling Char

Environmental DNA sampling (eDNA) has emerged as a powerful tool for detecting rare aquatic animals. Previous research suggests that eDNA methods are substantially more sensitive than traditional sampling. However, the factors influencing eDNA detection and resulting sampling costs are still not well-understood. Here we use multiple experiments to derive independent estimates of eDNA production rates and downstream persistence from Brook Trout (Salvelinus fontinalis) in streams. We use these estimates to parameterize simulations comparing the false negative detection rates and relative cost of eDNA sampling and traditional backpack electrofishing. We find that despite the high variation in eDNA production rates and downstream persistence – both of which influence detection probabilities – eDNA sampling is substantially more sensitive and less expensive than traditional electrofishing for determining the presence of rare Brook Trout.