The origin of Christ being depicted symbolically in the form of a fish can be found in the catacomb art of the earliest Christians. Fish feature constantly in the New Testament - many of the apostles were fishermen, later appointed to become \"fishers of men\", the miracles of the loaves and fishes, and the miracle after Christ\'s resurrection, where Peter was asked to throw his nets in one more time. By a very clever coincidence, the letters making up the Greek word for fish ????? (ichthys) are also the starting letters for \"Jesus Christ, Son of God, Saviour\".
Once Roman persecution ended, and iconography was free to develop, purely symbolic representations of Christ were no longer considered appropriate. As He had become incarnate, therefore it was necessary and proper to depict Him as the God and Man that He was revealed to be. Thus the fish symbol for Christ quickly disappeared. Why use a symbolic representation when we have the \"real thing\"?
It is interesting that this symbol began to be used in very recent times by various non-Orthodox churches and groups. Everything old is new again .... As for its use by cults, I can\'t offer anything on any geometric or mystical significance it may have for them, perhaps it varies with each cult\'s beliefs.
