‘Huge Problem’ of 70k barriers in rivers across UK

But data on Northern Ireland is scarce, with less than 100 obstacles recorded on the country's thousands of kilometres of rivers.

Weirs, concrete dams, underwater gates and other barriers - many of which are "old, redundant" installations that serve no practical purpose - make it difficult for fish and other wildlife to migrate, create areas of concentrated pollution and affect the overall health of the habitat, WildFish said.

A new database compiled by the environmental charity reveals there is an average of one manmade barrier for every 2.5km (1.5 miles) of waterway across 150,000km (93,000 miles) of rivers across Britain.

These manmade river obstacles are eight times more prevalent than natural barriers such as waterfalls, which only occur around once every 20km (12 miles) on average, WildFish said.

Barriers can damage the entire river ecosystem, with 674 rivers in England failing to achieve good ecological status in 2023 due to blocks to fish migration, the charity said.

River blockages are a driving factor in declines for four of the seven British freshwater species that are at risk of extinction - Atlantic salmon, European eel, allis shad and twaite shad.

But when barriers are removed, rivers can quickly restore their flow and fish return, WildFish said.

The charity is calling for government action on removing barriers where possible to help restore wildlife.