The Hildebrand Rarity by Ian Fleming (1960) Jonathan Cape

A wealthy man, Milton, gets Bond and another man, Krest, to help him in searching for a rare variety of squirrel fish.  On the way to where they want to search, Milton turns out to abuse, physically and verbally, everyone on board, especially his wife.  When the fish is found, Milton poisons the water to capture it.  That night, Krest is found to have been murdered by stuffing the rare fish down his throat.