A BIG salmon was filmed swimming near the Diglis Fishway viewing window.
The video, shared by the Unlocking the Severn team, shows the fish stopping to linger outside the window before returning behind the wall, leaving its tail exposed.
Salmon is just one of the many species of fish that have been sighted at Diglis Fish Pass.
Other species that had made appearances at the viewing window include the endangered twait shad and sea lampreys (also known as vampire fish).
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According to Unlocking the Severn, the salmon tend to spawn in November and December in spawning grounds they dig into gravel substrate in the shallow headwaters of the rivers.
Salmon are not randomly distributed in our seas, but rather follow very narrow migration routes along our coasts to reach their North Atlantic feeding grounds.
The Diglis Fish Pass contains a room under the River Severn, with a large viewing window where fish can be seen making their way upstream.
Two cameras are set up in the observation room, both monitoring every passing fish.
The viewing window is backlit so the cameras can detect fish at any time of the day.
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What is a fish pass used for?
The purpose of a fishway is to allow fish to pass man-made blockages in the water. At Diglis, the weir means that many fish looking to swim upstream struggle because of the two-metre separation.
The pass consists of 11 small pools, each only 20cm higher than the previous one, making it easier for fish to cross.
Fish sense the current of water in the river and can swim up, the walls of each pool relieving some of the force created by the water.
The Diglis Fish Pass relies on volunteer staff who offer tours which can be booked through the Unlocking the Severn website.
For more information on ticket availability, you can visit the Unlocking the Severn website at www.unlockingthesevern.co.uk.
. Big salmon filmed by Unlocking Severn Diglis Fish Pass