What other victories other than catching the marlin were achieved by Santiago?
Hemingway's The Old Man and the Sea is clearly a story of perseverance and determination. Victory implies something much more intense, but Santiago does experience some kinds of victories through his perseverance and determination.
You mention his catching the marlin. That's the first victory, of course, for he has been eighty-four days without a fish. He has broken his dry spell (his unlucky time) simply by catching the marlin. The second victory is actually being able to haul it in by himself. This fish, his brother, is gigantic, and it is no easy feat for him to prepare the fish and the boat for their trip home. The third victory is similar--he manages to keep focused and intent despite his mental wanderings and physical struggles. Finally, Santiago experiences a victory in the eyes of the boy who so adores him. Manolin had not lost faith in the old man, but this is a reminder that Santiago is still the finest fisherman.
Others who see the floating carcass are impressed or pitying or saddened at the sight; for Santiago it is victory enough to know he caught the fish and he is no longer unlucky.