A snail-eating Irish trout whose name derives from the deep red spots on its sides (Giolla Rua is the Irish for “red fellow”). It is apparently the only fish that has a gizzard (of sorts) to aid digestion. This anatomical curiosity lies behind the story that a priest, presented with a gillaroo on a Friday, refused to believe that it was not chicken and would not eat it; ever since, the fish has been considered cursed and unfit to eat.