1. The fish hanging to the right seems to be a symbol for the moon. The tail is a clear sign of that.
2. And there is a complex connection from what I presume to be the sun (left) to this fish-moon (right). The idea perhaps is to tell that the moon is illuminated by the sun.
3. The mouth of the fish is different from the mouth of similar fishes during the Waxing Moon. May we read this mouth in the form of a double apex as a sign of the Waning Moon?
4. That the moon is waning is also seen in the head down direction of the fish.