Why has the boy been ordered not to fish with the old man?

Santiago, who has gone eighty-four days without a catch. He has a single friend, a boy named Manolin, who helped him during the first forty days of his dryspell. After forty days, though, Manolin's parents decide the old man was unlucky and ordered their son to join another boat. Despite this, the boy helps the old man to bring in his empty boat every day.