The meanings, origins and ancient traditions surrounding Christian symbols date back to early times when the majority of ordinary people were not able to read or write and printing was unknown. Many were 'borrowed' or drawn from early pre-Christian traditions. No Fish is mentioned by name either in the Old or in the New Testament. Fish abounded in the Mediterranean and in the lakes of the Jordan, so that the Hebrews were no doubt acquainted with many species. Two of the villages on the shores of the Sea of Galilee derived their names from their Fisheries, Bethsaida (the "house of Fish") on the east and on the west. There is probably no other sheet of water in the world of equal dimensions that contains such a variety and profusion of Fish. About thirty-seven different kinds have been found.
The Definition and Meaning of the Ichthus / Fish as a Catholic Christian Symbol
Using the Ichthus acronym IChThUS means "Jesus Christ, God's Son, Savior".
The Ichthus / Fish was chosen as an early secret Symbol indicating that the person who knew the meaning of the Ichthus was a Christian and safe to associate with. Being a Christian was extremely dangerous for hundreds of years following the life of Jesus due to the persecutions of the pagan Roman Emperors.
The sign of the Ichthus
It was not necessary to point the fish in any particular direction, the basic symbol was sufficient:
Reference to the Ichthus / Fish Christian Symbol in the Bible
Fish are called called 'dag' by the Hebrews, a word denoting great fecundity (Gen. 9:2; Num. 11:22; Jonah 2:1, 10).
Ichthus / Fish Christian Symbol