From the book "How to interpret your own dreams" by Tom Chetwynd:
"Fish; the contents of the deeper layers of the unconscious mind. As one of the primitive ancestors in the scale of evolution, it refers to the remote past, and comes from a profoundly alien underworld. The saving power of renewal and rebirth may be symbolized by fish, which are often the equivalent of the treasure in the depths of a cave or well. If the fish has some spiritual quality about it: The Self. "