Santiago begins to talk to the fish and even plead with it to take the bait. What can you infer about him during this sequence?

The dynamic between the fish and Santiago is interesting. In many ways the fish is Santiago's saviour. Catching it would mean he feels his younger more youthful self. Catching it means he is not just a decrepit old man, the butt of jokes. Yes, catching the fish would mean a communion of sorts with something he believes to be his brother, his life and his saviour.