Twait shad

The twait shad or twaite shad ("Alosa fallax") is a fish. It was much eaten, and thought to be one of the best-tasting fish. 
Its life style is rather similar to the salmon. The adults live in the eastern Atlantic and Mediterranean, but come up rivers to breed. They have vanished from the dinner table because the Victorians build weirs in the Severn which stopped the fish getting to their breeding grounds The Severn, in SW England, is vital to the fish. It is by far the largest river opening in that part of the Atlantic. Overfishing, pollution and habitat destruction have also helped the shad's decline.
Now, ways round the weirs are being built, so the fish can once again reach its ancestral breeding grounds.