A dead fish is read symbolically as a feeling or hope that has run out of life, or an idea that has gone stale; it is about the inner world, not a forecast. Because fish usually stand for emotions moving below the surface, a fish floating belly-up suggests a feeling you have stopped tending. Many dead fish in a lake or on a shore are read as disappointment spread across one area of life. A dead fish at the market or in your kitchen is taken as something that looked useful but has gone off. Throwing it away is read as clearing space for something fresh. The dream may ask where your energy has gone flat.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.