Trust unlocks UK's longest river for endangered migratory fish

This May, for the first time in nearly 180 years, the UK’s longest river has been unlocked for the epic spawning migration of an endangered fish, the twaite shad. An ambitious conservation project has unlocked the length of the River Severn, reconnecting ancient spawning grounds for this once-prolific fish.

Diglis fish pass, Worcester Diglis fish pass, Worcester

Four huge new fish passes now provide a route around weirs that have thwarted fish migrating up the river since Victorian times. Shad normally visit the river in May; their colloquial name is May Fish and May Day marks the official start to the shad run. This May dawns on a new era of hope for the endangered May Fish and all fish migrating on The UK’s longest river.

Sign of spring

The annual shad run was once a celebrated sign of spring along the Severn. Shad fish were known and loved by kings and commoners alike. Severn shad were ordered for Henry III’s royal court in London. But, arriving en masse during the spring hunger gap, shad were also a lifeline for local people. When the River Severn still followed freely, hundreds of thousands of shad migrated from the sea up the river each year to spawn. They swam at most hundreds of miles to the upper reaches of the river in the Welsh borders.

Industrial revolution

But shad’s fortunes changed completely when the Industrial Revolution claimed the River Severn as an artery for industrial trade. In the 1840’s navigation weirs were built right across the river which created more reliable, deep passage for large barges carrying industrial goods between the Black Country and the docks at Gloucester. But for shad the weirs were a barrier that suddenly and catastrophically cut short their migration. Shad could no longer reach their spawning grounds in gravel beds further upriver. As a result, the local population crashed in size. Now only a small residual population of twaite shad migrate onto the River Severn each May. Confined downstream of Worcester, 35 generations of fish were left to spawn as best they could in the deep, fast-flowing waters of the river’s lower reaches.

Underwater gallery

However, the Unlocking the Severn project has recently completed a series of four massive fish passes alongside navigation weirs on the River Severn between Worcester and Stourport. An additional two partial weir removals have reconnected further ecologically rich habitat of the River Teme (a tributary that joins the Severn at Worcester). In total, the project has restored access to 158 miles of vital river habitat for wild fish of the River Severn. Uniquely, the new fish pass at Diglis in Worcester includes an underwater viewing gallery allowing scientific monitoring of endangered migrating fish. Members of the public can also book a guided tour for their chance to see wild fish swimming by.

Challenges for freshwater fish

Projects like Unlocking the Severn are vital at this time, as the wider environmental context for freshwater wildlife remains perilous. Freshwater species face big challenges of habitat degradation and loss, over-exploitation, and climate change. In this context, being able to move between patches of good habitat – known as connectivity – is vital for threatened wildlife to survive.

So, as May blossom froths in the hedgerows and May flies dance above the water, it’s good to know that there is new hope for the May Fish’s epic spring migration within the UK’s longest river. In addition to the twaite shad, the new fish passes will help to secure the long-term future of other endangered fish species such as salmon, eels, and lamprey.

Putting right a wrong

Jason Leach, Programme Director comments: “It’s thrilling to think that after so many years, we’ve put right a huge wrong to River Severn wildlife. With the help of modern engineering, we’ve restored the connectivity that Victorian river engineering took away. The shad can now access their ancient spawning habitats once again and we look forward to witnessing the recovery of this courageous fish!”

The biggest conservation project of its kind in Europe, Unlocking the Severn is delivered by Canal & River Trust via partnership with Severn Rivers Trust, Environment Agency and Natural England and is made possible with funding from the National Lottery Heritage Fund and the European Union LIFE programme.