World's Biggest Fish - the great whale shark in Western Australia

International Wildlife, Jan, 1999

Why tourists and researchers are flocking to Western Australia to swim with school-bus-sized whale sharks

My god, look at the size of that one," shouts skipper Mark Small. An enormous gray shadow as big as a bus passes silently by the bow of our boat as we motor in the Indian Ocean two miles out from the coast of Western Australia.

Nervous anticipation runs through the boat's passengers, a mix of tourists and scientists. We are about to jump overboard to swim with whatever is out there.

Small whirls the helm and calls out to a crew member to keep an eye on the marine leviathan. Even veteran shark-watchers such as marine biologist Dennyse Newbound are keyed up. "This is always the anxious moment for me," says Newbound, a University of Western Australia graduate student. "Is it a whale shark or not?"

Hopes of seeing a whale shark have drawn all of us here to Ningaloo Reef, a marine park near the town of Exmouth. Despite its plankton diet, passive nature and enormous size (as much as 17 tons), the whale shark is not a species of whale. This cold-blooded giant is a shark--the world's largest fish. And we want to meet it up close.

Some of us are here for the sheer thrill of the encounter; others, to learn more about this little-known creature. Even though they are big, whale sharks are elusive. Until the 1980s, few people had ever seen one. Then came the discovery that some of the fish gather yearly at Ningaloo, a finding that sparked the development of an ecotourism industry here.

Now, along with the adventuresome tourists, scientists such as Newbound are coming to Ningaloo to answer basic questions: How long do they live? How large do they get? How many of them are there? Most important, Newbound wants to know if these whale sharks stay near the Australian coast or migrate to other areas where they may be hunted.

For a few months every year, a group of these large filter feeders come to this reef 850 miles north of Perth. Here the sea bottom plunges from 30 to 600 feet; the continental shelf meets the deep ocean's cold, nutrient-laden currents; and the color of the water changes rapidly from robin's-egg blue to dark indigo. The whale sharks usually start arriving a few weeks after the first full moon in March, creating a predictable shark-watching season each austral fall. This year, however, the sharks are nearly two weeks late, worrying the 14 licensed tour-boat operators who charge more than $200 per person to snorkel with them.

Fortunately for us, the dry spell breaks. A search plane radios in the location of large, tadpole-shaped shadows, and we head for a site out in the open ocean. But before we reach it, the captain spots what appears to be another whale shark. The crew moves into action: One crew member (called a "spotter") jumps overboard and swims over to identify and pinpoint the creature, while Small maneuvers us into its path.

As we prepare for the signal to dive, Newbound reaches for the sheath strapped to her shin and stows away her most crucial item: a pair of tweezers. She will use these to remove a sample of quarter-inch-long crustaceans called copepods from the skin of the whale shark. With the aid of these tiny parasites, she hopes to help solve at least one mystery about Ningaloo's whale sharks: Where do the fish go when they leave this reef in late May?

Some researchers, such as shark biologist John Stevens of the Commonwealth Scientific and Industrial Research Organisation in Tasmania, suspect these sharks may travel to Christmas Island, south of Java, to feed during an annual crab spawning there. Stevens, who literally wrote the book on sharks in Australia, thinks that whale sharks are opportunists, taking advantage of mass spawnings to scoop up bumper crops of food from different locations.

Whale shark research is still in its infancy. Until three years ago, scientists did not even know if these sharks laid eggs or bore live young. (Whale sharks actually do a combination of both, creating eggs that hatch inside their body.) Researchers know that the sharks are also found in warm waters off North America, Africa, Southeast Asia and elsewhere, but no one knows their total population, or whether their numbers are increasing or decreasing. As a result, no one can say if they are endangered. But threats loom: In Taiwan, the Philippines, Thailand and Indonesia, fishermen have been killing several hundred of these animals per year. Middlemen sell the fins to Taiwanese restaurants for $100 per pound. (Whale shark hunting was recently outlawed in the Philippines, but some conservationists doubt this will stop the practice.) "A hundred whale sharks killed may not sound like a lot," Newbound says, "but it could spell trouble if their numbers are already low."

Before anything can be done to safeguard Australia's whale sharks, biologists need to know where they travel. Perhaps the sharks drift just out of sight off the coast and then return to Ningaloo occasionally to gobble up plankton. Or they may migrate from west Australia to Christmas Island to Indonesia and the Philippines.