A POPULAR city attraction is hosting a free open day on an upcoming Bank Holiday.

The Diglis Fish Pass will be open to all visitors on a drop-in basis for Monday, May 1 to celebrate the 'Severn Shad Run’.

The day will commemorate the return of the endangered twaite shad fish to the river Severn.

The twaite shad, or May Fish , migrate into freshwater, with May 1 selected as the Unlocking the Severn project's day to celebrate their return.

READ MORE: Diglis Fish Pass and Diglis Island tours reopening for 2023

Those attending will have the opportunity to travel beneath the surface of the river into the underwater viewing gallery for a chance to spot some fish swimming by.

The fish are not always guaranteed to be at the viewing window but tours this spring will coincide with the spring migration, where shoals of fish undertake their spawning migration upstream.

There will only be 18 people allowed in the viewing gallery at any one time, so queues may form on the day and timeslots may be issued.

The viewing gallery is accessible via a flight of 36 steps. and children must be supervised by an adult at all times.

READ MORE: Take a look inside the Diglis Fish Pass

At the time of construction, the Diglis Fish Pass was the largest in England and Wales, and already provided 25 species of fish with improved access to habitats along the river.

The purpose of a fish pass is to allow fish to move past manmade blockages in water. In Diglis, the weir means that many fish looking to travel upstream struggle due to the two-metre separation.

The pass consists of 11 small pools, each just 20 cm higher than the last, making it more manageable for the fish to swim through.

The fish detect the stream of water in the river and can travel upwards, with walls in each pool relieving some of the force created by the water. 

Unlocking the Severn is a conservation and river engagement project being delivered by Canal & River Trust, with partners Severn Rivers Trust, Environment Agency and Natural England.

This project is funded from the National Lottery Heritage Fund and the European Union LIFE programme.