Baseline ecological data is essential for measuring the impact and success of any biodiversity management strategy.

Very little was known about fish populations in the River Ock catchment. Freshwater Habitats Trust (FHT) needed to gather fish community data quickly across the landscape, so it could take action on local pollution issues and monitor the results over time.

Working with the Ock Arable Project, FHT used NatureMetrics aquatic eDNA kits to survey the River Ock and six of its tributaries in a single field visit. The survey produced a valuable baseline to measure the success of pollution mitigation against.

Building a baseline across a complex landscape

The Ock catchment covers a dispersed mix of springs, headwaters, ponds, small lakes, streams and rivers. FHT urgently needed baseline fish data to address pollution issues and monitor the outcomes of its management interventions.

The team needed a rapid, non-invasive survey method that could cover this varied landscape without specialist sampling expertise.

Rapid surveying without invasive techniques

NatureMetrics provided aquatic eDNA kits to the Ock Arable Project and FHT. The kits are easy to use, so a project ecologist with no prior sampling experience could collect samples quickly while on site.

Seven samples were taken, one from the River Ock and one from each of six tributaries. Together they gave a broad geographic spread across the catchment from a single, non-invasive field visit.

The seven eDNA samples detected 11 fish taxa from 6 orders, 7 families and 11 genera.

• Three-spined stickleback (Gasterosteus aculeatus) was the most commonly detected species. It is a native fish found widely across Britain and Ireland.
• European bullhead (Cottus gobio) is listed on the IUCN Red List and under Annex II of the EU Habitats Directive (SAC species). It is an important indicator of freshwater ecosystem health.
• Brown trout (Salmo trutta) is a popular commercial and angling species, and another key indicator of freshwater health.

A baseline for measuring and protecting biodiversity

• A benchmark for pollution mitigation: FHT now has a fish community baseline to measure the ecological response to pollution measures against over time.
• Species of conservation significance identified: The detection of European bullhead and brown trout highlights the catchment’s ecological value and gives FHT clear indicators to track.
• Proof that eDNA scales: The project showed that comprehensive fish data can be gathered quickly across complex freshwater landscapes without invasive methods or specialist teams.
• Plans to grow the monitoring: FHT plans to introduce regular eDNA monitoring across the Ock catchment, which could expand to amphibians and invertebrates. It also plans to run side-by-side comparisons with conventional fish surveys to further validate the approach.