In Musèe des Beaux Arts by W.H. Auden the people on the ship do nothing after seeing Icarus fall into the sea and the ship continues on its way. Why was that? Because according to the author, when a tragedy happens, human beings are not affected by it if their interests are protected and they have an horizon to pursue.
The fish died, because, using context clues, the word mournfully is usually associated with death or someone/ something leaving, and since a fish couldn't swim away, we would have to believe that the fish has died.
The story is told from the view point of the story's protagonist, Thomas.
