The fish is a symbol of the early Christians, and of Jesus, called the Fisher King, and the Fisher of Men. It has been seen on antique urns, steps of Turkish basilicas, and Volkswagens.
The fish is also a symbol of the zodiac sign Pisces. This is a water sign which is seen as artistic and sensitive, sometimes emotional in the extreme.
Astrology and religion collide at last, and what do we learn? I'm not sure. I don't like seafood.