In Ancient Rome the fish could have many meanings and uses. In the Defense of Apuleius the writer has to defend himself against charges of magic and witchcraft due to the fact a certain type of fish was found in his house. Fish were also very important to the mediterranean diet as Fish Sauce was a key flavouring in the Ancient World.
In addition, the symbol of the fish was associated with the Greek god, Orpheus, who was described as a “fisher of men”. The descent of Orpheus into the underworld to save the soul of his lover, Eurydice, also became a metaphor for Christ the Saviour.
For more information about the meanings of animals in Roman art, see our relevant blog post: Animal Symbolism in Roman Art.