BOLTON-LE-SANDS 34A - Elver tidal flap

Elver tidal flap at Red Bank Farm, Bolton le Sands on the Lancashire coast.
The tidal gates introduced after WW2 to prevent flooding and reclaim land for farming, also prevented returning elver migrate up the rivers to mature into adult eels before returning to the Sargasso Sea to breed.
This is one of 11 tidal flaps inserted into the gates in this area to allow the elver access to the watercourses necessary for their mammoth migration.