Abstract
Estuarine ecosystems are among the most productive and ecologically important environments, supporting diverse fish communities through habitat connectivity, nursery function, refuge provision and feeding opportunities. However, pressures including urbanisation, habitat degradation, shoreline modification and climate change have altered the structure and function of many estuaries. The Thames Estuary has experienced extensive historical habitat loss and modification, with consequences for fish communities and wider ecosystem resilience. Although restoration and habitat-creation projects are increasingly being implemented, their effectiveness in supporting fish biodiversity and habitat function remains uncertain.
This study will examine fish community responses to intertidal habitats of differing condition, such as natural, degraded, restored and created across the Thames Estuary. Environmental DNA metabarcoding will be used as the primary tool to assess fish community composition across 25 sites in spring 2026 and spring 2027. Paired fyke-net surveys at a subset of 10 sites will provide direct evidence of local fish occurrence, size structure and habitat use, and will help interpret eDNA detections. Environmental variables, including salinity, temperature, turbidity and dissolved oxygen, will be measured to assess how physicochemical gradients shape eDNA-detected fish communities alongside habitat condition. Stable isotope analysis will be included where sufficient fish tissue samples are available, using a tiered approach: within-species comparisons for common taxa where possible, community-level isotopic niche metrics where mixed samples are sufficient, or descriptive isotope biplots where sample sizes are low.
The project will also include a seagrass restoration component, using eDNA metabarcoding to assess fish community development across restoration stages, natural reference meadows and paired bare-sediment controls.
By linking eDNA-based community composition, functional guilds, paired fish-capture evidence and environmental gradients, this research will provide new insight into how restored and created habitats support fish biodiversity and habitat function. The findings will inform evidence-based restoration monitoring and management strategies aimed at enhancing ecological resilience, connectivity and fish habitat value across the Thames Estuary and associated coastal restoration sites.
Example habitats
