Answer:
The theme of the Fable about the dog and the stream is all about greed. That the inability of one to contain his greed will lead to problems for the person in question.
This could be seen in the dog losing the piece of fish in his mouth just because of seeing his shadow that projected an image of him having a bigger portion. On the long run, being contented with the little the person has is far better than being greedy.
Explanation: