Fish played a big role in the early church. You might be surprised how often fish are mentioned in the New Testament. A drawing of a fish was one of the first Christian symbols. Being a Christian was illegal in those days, so Christian had to have sercret passwords so that they could recognize one another without other people recognizing who they were. One of the languages early Christians used was Greek. The Greek word for fish, ICTHUS, contains the first letters of the phrase, "Jesus Christ, Son of God, Savior," and so it became a kind of a secret password among Christians of the Roman Empire. Here is how the early Christians would use it. They would walk up to a person whom they thought might also be a Christian and draw half of a fish in the dirt with their foot as they talked. If the other person completed the drawing with a swipe of his or her foot, you could safely acknowledge your true beliefs.
[Source: Supplement, St. Paul Roman Catholic Cathedral, Saskatoon, SK, Canada; March, 2010]