Flood-Pulse Effects on Environmental DNA Detection of Fish Biodiversity in the Kavango River

Seasonal flooding changes fish habitat availability and the transport, retention and recovery of genetic material, complicating environmental DNA assessments in connected river–floodplain systems. This review examines how these processes may influence fish biodiversity detection in the Kavango River and develops a framework for interpreting seasonal surveys. Published regional research is evaluated alongside studies of DNA transport, molecular bias and imperfect detection. A deterministic model separates source production, discharge dilution, recovery efficiency and repeated sampling; its numerical outputs are illustrative and do not represent Kavango field observations. Under a constant source, a fourfold discharge increase reduces relative concentration to one quarter and lowers modelled single-sample detection from 0.777 to 0.313. Three independent samples increase detection to 0.989 under baseline conditions and 0.675 under the diluted scenario. These calculations show why changes in detections cannot be attributed to biodiversity change without accounting for the observation process. We propose sampling the rising, high-water, falling and low-water phases across channel, channel-margin and connected floodplain habitats, supported by replicated water samples, contamination controls, inhibition testing and regional reference sequences. Flooding may increase the spatial coverage of DNA while weakening local attribution and reducing recoverable concentration. Hydrologically explicit monitoring can improve interpretation, but the magnitude and direction of these effects require empirical validation in the Kavango River.