tuna eat fish & if an animal eats other animals for food , then the animal is the predator ->  tuna is a kind of predator  tuna is a kind of predator & tuna is a kind of fish ->  tuna is a kind of predatory fish  tuna is a kind of predatory fish & commercial harvesting from the ocean has caused populations of large predatory fish to decrease -> commercial harvesting from the ocean has caused the populations of tuna to decrease