What did Hemingway mean by "the setting of the sun is a difficult time for all fish"?

Question

In Ernest Hemingway's The Old Man and the Sea, the Old Man has hooked a huge marlin, which is pulling his boat out to sea. Meanwhile, using another line, he has caught a "dolphin" (meaning a dolphin-fish or dorado):

The old man unhooked the fish, rebaited the line with another sardine and tossed it over. Then he worked his way slowly back to the bow. He washed his left hand and wiped it on his trousers. Then he shifted the heavy line from his right hand to his left and washed his right hand in the sea while he watched the sun go into the ocean and the slant of the big cord.

"He hasn't changed at all," he said. But watching the movement of the water against his hand he noted that it was perceptibly slower.

"I'll lash the two oars together across the stern and that will slow him in the night," he said. "He's good for the night and so am I."

It would be better to gut the dolphin a little later to save the blood in the meat, he thought. I can do that a little later and lash the oars to make a drag at the same time. I had better keep the fish quiet now and not disturb him too much at sunset. The setting of the sun is a difficult time for all fish.

He let his hand dry in the air then grasped the line with it and eased himself as much as he could and allowed himself to be pulled forward against the wood so that the boat took the strain as much, or more, than he did.

What does the Old Man mean by the sentence in bold? What exactly is the Old Man worried over here? Why would fishes be "worried" at sunset?

Answer 1

Taking the phrase literally, sunset is a difficult time because it is a change of environment. Species that are adapted to hunt their prey using the light of the sun can no longer do so; species that are adapted to evade predators by eyesight must now suffer the attacks of electro-sensing animals like hammerhead sharks; species that hide in the depths during the day must make their way to the surface; and so on.

But in the context of the story, the Old Man is really talking about himself. The text emphasizes at several points the connection between the Old Man and the marlin: for example, the fish is moving “perceptibly slower”, and so is the Old Man (“he worked his way slowly back to the bow”). The fish is “good for the night” and so is the Old Man. And “the setting of the sun” is a metaphor for old age, which is a difficult time for fishermen like him.

Between his bad luck and his time of life there is an unavowed but strongly felt connection. The one seems to confirm the other, in his own mind as in that of his fellow fishermen. Even the boy whom he has lovingly instructed in their trade is advised by his parents to leave the old man alone. “The setting of the sun is a difficult time for all fish,” as the old man observes; and old age is a difficult time for active men.

_{F. W. Dupee (1953). ‘Hemingway Revealed’. The Kenyon Review 15:1, p. 151.}

A comment wonders whether we can compare the marlin to the Old Man, in cases where Hemingway does not explicitly make this comparison himself. I think that as a reader it is fair to “take a hint”, so to speak. Once Hemingway has introduced us to the idea that the two main figures in the story can be compared, we don’t need him to hold our hand in every case: we can take any claim about the one and consider whether it might apply to the other. (I quoted Dupee to show that this is a common approach to the text.)

Displacement of description from one thing to another is a common literary technique, whether it is displacement of an adjective from one noun to another (a transferred epithet), or displacement of an emotion from someone to their environment (the pathetic fallacy), so it’s something to always keep an eye out for.