The Symbolism of the Fish - ΙΧΘΥΣ (Ichthys)

Christian fish symbol

What is "Ichthys"?

Ι Iota	Χ Chi	Θ Theta	Υ Upsilon	Σ Sigma
Iesous	Christos	Theou	Yios *	Soter
Jesus	Christ	God's	Son	Saviour
			(* pronounced Iios - with emphasis on the 'o')

Clemens was a Greek theologian and noted that letters of the Greek word for fish, ΙΧΘΥΣ (pronounced Ichthys), made the following neat little acrostic:
So in addition to the simple and easily recognisable symbol, there is also a motto that describes Jesus as Christ, God's Son, and Saviour.

 As early as the 2nd century St. Clement of Alexandria suggested that Christians identify themselves with a seal depicting a fish or dove (Paedagogus, III, xi.) Even before that time, inscriptions on monuments suggest that the fish symbol was familiar to Christians.  

After Christ's crucifixion his followers were persecuted and the fish symbol was used as an identifying symbol that fellow Christians would recognize, but non-Christians would not. Therefore Christians could connect with each other through a secret code, such as a fish symbol, without revealing themselves to the oppressors.
By drawing one half of the fish in the dirt with their finger, a stick or their foot the Christian could learn if a stranger was friend or foe. If the party in question knew the "secret symbol " he would finish the other half of the Christian fish to identify himself as a fellow Christian.
When you stop to think about it this was ingenious. People can make patterns in sand or dirt very nonchalantly. It would have been a very good means of  covert communication -- remember, their lives were at stake. Christianity was against the law and punishable by death.

Early in the 4th century, when Emperor Constantine publicly declared that Christianity should be allowed, execution by crucifixion was abolished and the cross became the more prevalent symbol for Christians.

The fish is also symbolic of the fishermen Apostles, Andrew, Peter, and the Sons of Zebedee (John and James), whom Christ would make "fishers of men" (Mark 1:17 and Matthew 4:18,19). The archangel Raphael is often represented with a fish brought back to cure the aged Tobit of his blindness. The symbol of the fish is also a wonderful reminder of the miracle of the loaves and fishes and its prefiguration of the Eucharist. (Mark 8:5-9 and Matthew 14:16-21)
                                                           
 As early as the 2nd century St. Clement of Alexandria suggested that Christians identify themselves with a seal depicting a fish or dove (Paedagogus, III, xi.) Even before that time, inscriptions on monuments suggest that the fish symbol was familiar to Christians.
 

SOURCES:
CatholicNotebook
CatholicCity.com
NewAdvent.com
CatholicReference.net
Seiyaku.com


Footnotes:
*1  Carl Liungman's magisterial volume 'Dictionary of Symbols 1991, W W Norton & Company, New York. p38