Does the old man change by the end of the novel? Does the fish change after it is captured? Why does the old man pursue the fish for so long?

Santiago sees the marlin as his last chance for salvation. He feels old and redundant. The other fishermen, with motors and radios, chuckle at the old man. The great Marlin is a shot at validation again, a reminder of who he was. We don't see a lot of Santiago after the ordeal. He is tired and the boy Manolin attends to him like an apostle to Christ. I don't think Santiago was meant to change. He is very much a Christ figure who returns from his own journey, at once victorious and defeated.