Dictionary of Ichthyology
Tobit's fish = the Book of Tobit in the Apocrypha tells of Tobit, who was blinded by sparrow dung while sleeping in a courtyard. The archangel Raphael told Tobit's son to catch a huge fish in the Tigris River and apply its gall to Tobit's eyes to cure his blindness. The fish was probably Luciobarbus esocinus, a large member of the Cyprinidae.