The BBC reports one of the UK’s rarest fish is getting a chance to return to its historical breeding grounds on the River Severn. The little-known twaite shad, a member of the herring family, was once common in British waters with thousands of the fish migrating upstream in spring. Numbers dwindled after weirs constructed in the 19th Century posed barriers to migratory fish. A conservation project is trying to unlock the river for fish by creating routes around several weirs.