The fish was originally a symbol of health, or, in old Ukrainian fairy tales, often helped the hero to win his fight with evil.
In the Greek alphabet “fish” (ICHTHYS) is an anagram of “Jesus Christ, Son of God, Savior”; it was a secret symbol used by the early Christians, and came to acquire Christian meaning in pysanky as well.
The fish represents now represents Christ himself. It is a popular motif on traditional Hutsul pysanky, and on diasporan ones as well.