Christian symbol Fish

Ichthys or Ikhthus is the Greek word for "fish." In English it refers to a symbol that resembles the profile of a fish, said to have been used by early Christians as a secret symbol and now known as the "sign of the fish" or the "Jesus fish."
Fish are mentioned several times in the Gospels. Several of Jesus' twelve disciples were fishermen.

Mark 1:17: "Come after Me, and I will make you become fishers of men."

Matthew 12:40: "...Jonah was three days and three nights in the belly of the great fish, so will the Son of Man be three days and three nights in the heart of the earth."

John 21:6: "And He said to them, 'Cast the net on the right side of the boat, and you will find some.' So they cast, and now they were not able to draw it in because of the multitude of fish."

Corinthians 15:39: "All flesh is not the same flesh, but there is one kind of flesh of men, another flesh of beasts, another of fish, and another of birds."

Matthew 13:47-50 "Once again, the kingdom of heaven is like a net that was let down into the lake and caught all kinds of fish. When it was full, the fishermen pulled it up on the shore. Then they sat down and collected the good fish in baskets, but threw the bad away. This is how it will be at the end of the age. The angels will come and separate the wicked from the righteous and throw them into the blazing furnace, where there will be weeping and gnashing of teeth."

John 21:11 "Simon Peter climbed aboard and dragged the net ashore. It was full of large fish, but even with so many the net was not torn."

The ichthys is seen in first century catacombs in Rome. According to tradition, ancient Christians, during their persecution by the Roman State in the first few centuries after Christ, used the fish symbol to mark meeting places and tombs, or to distinguish friends from foes.