The Flathead Catfish (Pylodictis olivaris) is a large species of North American catfish, known for its flat head and wide mouth. These fish can grow over 5 feet in length and weigh up t... The Flathead Catfish (Pylodictis olivaris) is a large species of North American catfish, known for its flat head and wide mouth. These fish can grow over 5 feet in length and weigh up to 123 pounds, making them one of the largest freshwater fish in their habitats. They are predominantly nocturnal, living in deep pools of rivers and lakes and preying on fish, invertebrates, and even other catfish. Their large size and aggressive nature make them popular targets for trophy anglers.Click here to read more about Flathead Catfish.