The "Diner Fisherman" is a resident of Arcadia Bay. He is sitting at a booth in the Two Whales Diner.
Episode Two - "Out of Time"[]
Max Caulfield can ask him if he caught any big fish today. He responds by saying that if by "big" she means "none", then sure, "he caught a lotta big ones today". Afterwards, he says that she should let him mourn over his eggs.
While Max is waiting for her breakfast, he gets up and changes the music on the jukebox.
Episode Five - "Polarized"[]
He appears in the diner sequence of Max's nightmare, looking at the fish trophy. If Max chooses to sacrifice Arcadia Bay, he is presumed to have died in the storm.