Unlocking the Severn LIFE project: eDNA monitoring of restoration effects on the River Severn (Phase II).
Abstract
The 'Unlocking the Severn' project aimed to assess the ecological impact of restoring river connectivity in the River Severn through the creation of fish passes at four weirs between Diglis and Lincomb. Specifically, the project focused on investigating changes in fish community composition and distribution using eDNA metabarcoding approaches. Samples were collected from the River Severn and the River Thames to map the distribution of shad (Alosa spp.) eDNA and assess fish community structure. Results showed successful negotiation of weirs by shad during the spawning season, indicating habitat reconnection. Fish and invertebrate community structures differed significantly between the Severn and Thames rivers. The study underscores the utility of eDNA metabarcoding for monitoring restoration effects on fish communities and suggests the establishment of a long-term monitoring program for consistent coverage. Additionally, incorporating hydraulic modeling approaches into surveys and reviewing existing metrics for invertebrate eDNA could enhance future monitoring efforts.