Gentle Giants of Taiwan's Seas-Whale Sharks

In July 2001, the Fisheries Administration of the Council of Agriculture began putting up whale shark "wanted" posters at harbors all around Taiwan's coasts. The words "If You Catch Me, Report Me" in large characters, along with the distinctive shape of the whale shark with its broad, flattened head, square snout, and large, wide mouth, make for an eye-catching sight amid the blue and gray hues of a busy port. "Fishermen should report all catches of whale shark to the local county or city government. Your valuable information is the best way for us to understand them, and will be a great step towards promoting marine conservation and a sustainable fishing industry." In addition to these words of friendly exhortation, however, the small print on the posters continues: "Non-compliance is punishable by fines of NT$15,000-75,000 under the Fisheries Law."

The meat of the whale shark is a whitish color like tofu, so Taiwanese fishermen call whale sharks "tofu sharks." Sharks play the role of predators in the marine ecosystem, and humans generally think of them as ferocious killers. But in fact the whale shark is the most docile of all the 370 known living shark species, and is not innately aggressive. The whale shark is known to science as Rhincodon typus, and is classified taxonomically as the sole member of the family Rhincodontidae.

Unlike the majority of sharks, with their tapered body shape and fearsome pointed teeth, the whale shark has an extremely broad, flat head, and its large mouth, which is as wide as its head, is without sharp-pointed teeth. Whale sharks are "filter feeders": as they swim through the water, they hold their mouths open to strain out plankton, crustaceans, and small schooling fish such as sardines or mackerel. They are also able to actively suck water into their mouths to feed.

Assistant Professor Joung Shoou-jeng of the department of fishery science at National Taiwan Ocean University has been researching sharks for over a decade. He says that although whale sharks are certainly "big eaters," they use their food extremely efficiently. A large proportion of the whale sharks caught by fishermen have empty digestive tracts. "They are not like many mammals, which excrete more the more they eat, and use resources very uneconomically," Joung emphasizes.

Another striking feature of whale sharks is the conspicuous pale markings arranged in a checkerboard pattern on their broad, dark backs. Whale sharks have very acute vision, so zoologists speculate that the patterns may help individuals to recognize each other. They may also protect against harmful ultraviolet radiation during the sharks' frequent activities close to the surface.

Whale sharks prefer to remain in areas with a sea surface temperature of 21-25oC, so they are mostly found in warm-temperate and tropical oceans within 30 degrees north or south of the equator. Apart from the waters of the West Pacific off the Philippines, Taiwan and Japan, whale sharks can also be seen swimming freely in the South Pacific, the Caribbean, and along the coasts of the Indian Ocean.

Whale sharks mostly travel alone, and often linger along coral coasts. Australian researchers surmise that the reason why the sharks appear around Ningaloo Reef on the coast of Western Australia from March to May each year is that this is when the corals spawn, releasing huge numbers of eggs. This increase in "primary productivity" attracts many shoals of fish, and these in turn are tracked down by the whale sharks, adding another link to a diverse food chain. Because the whale sharks' tastes in prey are very similar to those of valuable commercial fish species such as tuna, fishermen from many countries look out for the presence of whale sharks as an important indicator of a potential high-value catch.

Similarly, around the island of Taiwan there are two annual peaks of whale shark activity, from March to May and from October to December. The sharks follow the rich pickings of food along the Kuroshio Current, and linger along the east and north coasts of Taiwan, frolicking as they slowly advance. Thus they often blunder into set nets placed along the coast by fishermen. Because they have no fear of humans, and love to get close to fishing boats, they also easily fall prey to harpoon fishers, and are regarded by fishermen as marine Dumbos.

Back when ocean fish stocks were still abundant, whale sharks, with their coarse, tough meat and their low-quality fins compared with other shark species, had little commercial value. "Until the 1970s, if fishermen out at sea happened to come across a sizeable whale shark, they would be terrified that their boat would be dragged along by it and perhaps capsize, so they did their best to steer clear of them," says Joung Shoou-jeng.

But in recent years, as fish stocks have dwindled, and with restaurateurs doing their best to develop new flavors, whale sharks have become very popular. Fishermen now vie to catch them, and the rapid decline in their numbers has pushed prices ever higher. According to a report from TRAFFIC Taipei, in 1985 a 3000-kilogram whale shark would fetch only NT$5000-8000, but by the late 1980s, the price of whale shark had rocketed to NT$150 a kilo, and a single shark could sell for the sky-high price of NT$2 million.

Because there are very few countries where people are in the habit of eating whale shark meat, Taiwan has become the world's largest consumer, according to TRAFFIC's report. A survey in India in 1996 showed that most of the meat of whale sharks caught by Indian fishermen was exported to Taiwan, South Korea and Singapore. According to Taiwanese customs records, the amount of whale shark meat imported into Taiwan each year is far greater than the amount caught by the island's own fishermen. Taiwanese fishermen even say openly that it was the Taiwanese who taught Filipino fishermen how to catch whale shark, and that many whale sharks also come onto Taiwan's market through illegal trading at sea between mainland Chinese and Taiwanese vessels.

When people who have seen whale sharks up close start talking about the behemoths, they always exude an air of wonder. According to records, a 20-meter-long, 34-tonne whale shark that was caught by Taiwanese fishermen off Lotung in Ilan County in 1987 was the biggest fish ever seen by humans. Joung Shoou-jeng, who has seen a hundred or more whale shark, says the largest he remembers was an 18-meter, 30-tonne leviathan that took skilled workers a day and a night to cut up.

Sadly, stories of such gigantic fish are no longer heard in Taiwan. New data published early this year by National Taiwan Ocean University shows that over the last five years, the average number of whale shark landed in Taiwan each year has remained at around 80, which is only a third of past numbers. An even more striking difference is the change in the size of the sharks. Over the past five years, they have averaged around four to five meters in length and something over 800 kilograms in weight. "They're all tiddlers!" exclaims Chen Chun-hui of the Taiwan Fisheries Research Institute, pointing at a statistical graph while speaking at a meeting of a fishing industry shark conservation team. Chen explains that whale sharks are not fully grown until they are at least ten meters long; thus all those caught in the last five years have been "children."

From research on whale shark DNA, Australian zoologists have discovered that whale sharks mature extremely late. They can live to over 100 years old, and only become sexually mature after age 30. Two females caught off the coast of India in the 1980s were nearly nine meters long, but neither had yet reached "puberty."

Different shark species have three modes of reproductive development: viviparous (giving birth to live young), oviparous (laying eggs in egg cases, to hatch on the sea floor), and ovo-viviparous (retaining egg cases in the uterus to hatch, and bearing live young). This differs from most bony fish, which produce millions of eggs at once. Interestingly, sharks, which are elasmobranchs (cartilaginous fish), practice "family planning." Many shark species produce less than ten young at a time. For many years, there had never been a pregnant female recorded among the whale sharks caught at different locations, and in many places only males have been seen. Although juvenile whale sharks had occasionally been discovered in the bellies of blue shark and marlin, details of whale shark reproduction, such as whether they are oviparous or ovo-viviparous, the ratio of males and females, or how large they are at birth, remained unsolved mysteries.

In July 1995, Taiwanese fishermen caught a 16-tonne, 11-meter female whale shark off Taitung. Joung Shoou-jeng, who hurried there after being notified by the fishermen, witnessed the shark giving birth-the first time this had been observed in the nearly 170 years since the whale shark was first described for science. The unfortunate female shark gave birth to 300 baby sharks at once. The little sharks, which were 40 to 60 centimeters long, covered the entire dock. Out of the water, only 15 survived. These were "adopted" by the National Museum and Marine Aquarium in Taiwan, and an aquarium in Japan, but most of them died within the space of six months.

This female shark also "spawned" the world's first scientific monograph on whale shark reproduction, which established that males and females are born in a ratio of more or less one to one. But this rare catch of a pregnant shark also confirmed how late whale sharks mature, and showed that in their reproductive strategy they prefer "quality" over "quantity." In today's age of unbridled exploitation of ocean fisheries, this does not bode well for the survival of whale shark populations.

Apart from the whale shark, two other gigantic members of the shark clan-the basking shark and the great white shark-have long been hunted in the West for fish oil and other products. In 2000, at the 11th conference of the Washington Convention (CITES), some countries proposed that the whale shark, the great white shark and the basking shark should be added to the list of species protected under the convention, to enable them to be more effectively conserved through international cooperation. But opponents of this move said that more scientific evidence should be produced before countries could be persuaded to act together to give legal protection to these species. The resolution was not passed on this occasion, but CITES actively required all member countries to carry out research on the natural history, migration routes and population distribution of whale sharks, with a view to devising rational management policies to regulate their exploitation.

In fact, whale sharks were never very abundant to begin with, and were never an important or regular source of catches for most countries' fishing industries. Hence the Philippines and India responded quickly to international calls for conservation, by banning the capture of whale sharks and trade in whale shark products. Following the decline in their numbers, whale sharks are today worth only around NT$20 million a year to Taiwan's fishing industry, so the conflict between conservation and fishermen's interests is much less than in the case of cetaceans. The fishermen themselves have also realized that the whale sharks they are catching are becoming "ever smaller and ever fewer." At a whale shark conservation team meeting at the beginning of this year, the presidents of the set net, tuna and other fishing associations gave their backing to the conservation measures being adopted by the Fisheries Administration.

"The purpose of conservation is not to ban fishing, but hopefully to allow resources to be used sustainably." Deputy administrator Shieh Dah-wen says that at present the Fisheries Administration hopes to be able to control whale shark catches by introducing just one of three possible measures: quotas, size limits, or a yearly close season.

To gain a better understanding of the whale sharks that migrate along Taiwan's coasts, the Fisheries Administration has commissioned National Taiwan Ocean University (NTOU) to carry out a program to track the sharks by satellite. Program director Joung Shoou-jeng says that last year the Council of Agriculture approved a NT$3.8 million budget for the program, and he plans to buy two whale sharks from set net fishermen. NTOU post-doctoral researcher Liao Yu-ya, who is assisting Joung with the program, says: "We have already designed two tailor-made satellite tracking devices to fit the sharks, costing NT$200,000 each, and we will tag and release the sharks this year. We hope to gather preliminary information on their migration routes, their preferred water temperatures, and so on." Now they are just waiting for suitable sharks to become available.

The paths followed by whale sharks on their travels through the oceans have still not been clearly identified. It is generally thought that they migrate seasonally, and that their movements are also affected by variations in water temperature, salinity, winds and tides. Whale sharks are tremendously powerful swimmers. They have three prominent ridges along each side of their bodies, which reduce drag as they move through the water. Their large, thick ventral fins and their unusual livers also play a role. In particular, the liver, which occupies two-thirds of the volume of the abdominal cavity, provides buoyancy, which helps the sharks to float up to play on the surface. But they can also dive as deep as 300 meters, which makes it very hard to establish whether they stay in a single sea area, or migrate between oceans.

Some researchers also maintain that whale sharks are very particular about water quality. Their gill structure is fragile and they need to keep moving in order to breathe. To date there have very few examples of humans successfully keeping whale sharks alive in captivity for long periods. This is another reason why people find it very difficult to learn more about whale sharks. But Australian "management" policies for the whale shark suggest a different approach.

In Taiwan, whale sharks' gentle and good-natured temperament makes them a "soft touch" in the eyes of fishermen. But in Australia, the sharks' docile nature has been made the basis for allowing humans and sharks to play together in the ocean. A 1997 report on whale shark ecotourism on the coast of Western Australia describes at length all kinds of assessment measures and rules for "close encounters" with whale sharks, such as limiting the number of boats that may approach the sharks when they visit the area each autumn, to avoid injuring them. The report also predicts that after the year 2000, whale sharks will generate NT$200 million a year in tourist income for Western Australia.

"The fact that whale sharks return to the same places each year not only allows researchers to observe particular populations over long periods," says Joung Shoou-jeng. "In Western Australia, in order to 'exploit' whale sharks as an ecological resource in the long term and allow shark tourism to develop stably, the tourism industry, the government and conservationists have joined together in a powerful alliance to protect the sharks and research them in depth."

Not only have the Australians gathered accurate information on the timing of the whale sharks' migrations, the locations they return to and their numbers, but researchers have also been able to record their distinctive body markings, which can be used as "fingerprints" to recognize individual sharks. Tourists who go out on shark-watching trips by boat can identify the animals they see through their binoculars, and learn about their temperaments and habits. Subject to strict rules, such as no flash photography and keeping a minimum distance, tourists also have the opportunity to dive and swim alongside the sharks. Some of the income from shark tourism is ploughed back into whale shark research. The report states that the entire cost of a survey of whale shark migration in the eastern Indian Ocean came from Western Australian tourist income.

To judge from Taiwanese fishermen's catches of whale sharks over many years, it is highly likely that there is a population of whale sharks that regularly migrates through the seas off Taiwan. Therefore it should not be impossible to develop similar seasonal shark-watching activities along Taiwan's east coast. But sadly, unlike whales, the Taiwanese public's conception of whale sharks has not gone beyond chunks of fish meat on restaurant platters, and the gigantic carcasses laid out in fishing harbors that get used as backgrounds for tourist snaps. "The important question is whether people can change their ideas about whale sharks, and reach out a hand of friendship so that the sharks can 'escape' the dining table and become good friends of mankind!" This what Joung Shoou-jeng hopes for.

Hammerhead shark. The whale shark is just one of over 300 shark species. There are many others which also have a long reproductive cycle and produce few offspring, for which humans have yet to show concern.

Seven years ago, a female whale shark, pregnant with 300 young, was caught off Taiwan. This catch revealed many secrets of whale shark reproduction for the first time, but all the baby sharks eventually died.