# Diurnal shifts in eDNA concentration of threatened juvenile river herring

## TL;DR

This study shows that sampling environmental DNA at night gives better results for tracking threatened juvenile river herring.

## Contribution

The study reveals that diurnal shifts in juvenile river herring behavior affect eDNA detection, with nighttime sampling being more effective.

## Key findings

- Nighttime eDNA concentrations of river herring were consistently higher than daytime concentrations.
- Consistency in sampling time is crucial if night sampling is not possible.

## Abstract

River herring,
Alosa
species, are threatened in North Carolina waters. Environmental DNA (eDNA) is a non-invasive approach to monitor their movement. River herring, particularly juveniles, are known to exhibit diurnal shifts within water columns. To assess how this influenced the detection of eDNA concentrations from fish, water samples were collected from the Roanoke River during the day and night of the same day for four weeks. Using qPCR analyses, we found that nighttime eDNA concentrations consistently exceeded those of daytime concentrations indicating night is a better time to sample. If night sampling is infeasible, consistency in sampling time is important.