They’re not whales at all, but by far the largest fish in the sea. Yet at nearly 50 feet in length and weighing 20 tons or more, they eat only the smallest marine animals. They are not a threat to humans, but their numbers are dramatically shrinking. Like elephants slaughtered for their ivory tusks, whale sharks are relentlessly pursued by poachers. From Africa to Asia, they are targeted for their meat and immense fins.