Quote 112
He could see the fish and he had only to look at his hands and feel his back against the stern to know that this had truly happened and was not a dream. At one time when he was feeling so badly toward the end, he had thought perhaps it was a dream. Then when he had seen the fish come out of the water and hang motionless in the sky before he fell, he was sure there was some great strangeness and he could not believe it. (4.80)
The word "strange" is associated with prowess and the respect it demands. Both the old man and the fish are therefore "strange."
Quote 113
But you enjoyed killing the dentuso, he thought. He lives on the live fish as you do. He is not a scavenger nor just a moving appetite as some sharks are. He is beautiful and noble and knows no fear of anything. (4.106)
The old man sees a lack of nobility in himself because he takes pleasure in destroying the beautiful creatures of the sea.
Quote 114
"They must have taken a quarter of him and of the best meat," he said aloud. "I wish it were a dream and that I had never hooked him. I’m sorry about it, fish. It makes everything wrong." He stopped and he did not want to look at the fish now. Drained of blood and awash he looked the colour of the silver backing of a minor and his stripes still showed.
"I shouldn’t have gone out so far, fish," he said. "Neither for you nor for me. I’m sorry, fish." (4.120, 4.121)
The old man does not regret killing the fish but rather the disgraceful end that the dead fish meets.