As creatures of the open ocean, whale sharks give biologists little opportunity for research. They do aggregate at certain coastal locations, though, and at Australia’s Ningaloo Reef Lara Marcus Zamora is helping to solve some of the mysteries surrounding them.
The whale shark is the biggest fish in the world. Its massive size (a large specimen can reach up to 18 metres long) and harmless disposition have fascinated us since the species was first discovered off the coast of South Africa in 1828 – and these two attributes have led to its popular tag of ‘gentle giant of the ocean’.
Mystery still surrounds this free-ranging animal that spends most of its time in open waters and out of our reach; studying it is not without its challenges! Luckily for us, though, whale sharks appear out of the blue every year and aggregate for several months at different coastal locations around the world, including Belize, Mexico, Australia, Philippines, Mozambique and the Red Sea. These seasonal gatherings are our only opportunity to approach the giants and learn more about them. My story with whale sharks started 10 years ago in the Seychelles where, in the waters of the Western Indian Ocean, I first encountered this unique creature. Swimming with a whale shark is a magical experience that no-one can ever forget, and from that very first moment the species has captivated me. With the encounter still fresh in my memory, years later I dedicated my PhD research to helping to unravel the mysteries of this giant. My main goal was to contribute any useful knowledge that I gained during my years as a PhD student to the effective conservation of whale sharks. Where do they come from? What do they eat? Why do they aggregate?
Ningaloo Reef on the north-western coast of Australia is one of the special places where whale sharks gather every year between March and July. It is characterised by two notable features: slopes that fall abruptly into the depths and a system of currents that makes the area very productive. Extending 260 kilometres along the coast, Ningaloo is the largest fringing reef in Australia and hosts a wide range of marine life, from reef fishes of all shapes and colours to mega-fauna such as turtles, manta rays, sharks and occasionally whales. Inland, Australia’s red desert, with its endemic species and jumping kangaroos, stretches to the horizon and far beyond. In this scenario the reef is the main attraction and diving, snorkelling and fishing are the most popular activities, bringing national and international tourists to the area all year round. A prosperous and well-regulated eco-tourism industry has developed around whale sharks at Ningaloo, generating a yearly revenue of about A$4-million (in 2006) that helps to support the local community.
Ecotourism operators have been working on Ningaloo Reef for several decades and provide researchers with first-hand information about the comings and goings of its marine inhabitants. From them we have learnt that whale sharks are no longer as gigantic as they used to be, and there are fewer of them too. These observations have raised some alarm in the scientific community, as shrinking size and decreasing numbers could well be signs that the species is being over-exploited.
Although the whale shark is protected in many countries, including Australia, and is classified as Vulnerable on the IUCN Red List of Threatened SpeciesTM, it is still hunted for food in South-East Asia, its white meat prized as a delicacy in Taiwan and its fins as an ingredient in soup by the Chinese. Its long life span – approximately 150 years – and low reproductive rate make it especially vulnerable to exploitation. The Ningaloo Reef population of this highly migratory species is very likely to be shared with some Asian countries, where strong regulations to protect the whale shark are not yet in place.
For the past 10 years Dr Mark Meekan, a shark expert at the Australian Institute of Marine Science, has led expeditions to Ningaloo Reef that have been a source of invaluable information about the numbers and structure of whale shark populations. Many scientists and students from different academic areas have participated in these field trips and for the past three years I have been one of them. Our field base is located in a remote area with expansive views over the ocean. An aluminium shed, struck by cyclones on several different occasions, serves as laboratory, living area and kitchen, and bats, birds and the usual snakes are our roommates. There are no luxuries there, but at day’s end the outstanding background of Ningaloo’s sunsets makes you forget about fresh water and a comfortable bed.
The spot and line patterns of a whale shark are easy to recognise from above, so we use a small plane in conjunction with a boat when we go out looking for our target animals. When a whale shark has been located by the team in the plane, for those aboard the boat it’s a time of excitement and nerves. Once in the water, we try to disturb the whale shark as little as possible, but there are many tasks to be completed. We photograph each animal for identification purposes and record its sex, size and any distinct markings that will also help to distinguish it. In this way, we have been able to recognise the same sharks year after year, including ‘Stumpy’, an old acquaintance of ours that has been sighted on and off since 1989!
Every year, hundreds of whale sharks congregate at Ningaloo Reef in Western Australia. Lara wants to know why. She believes that the secret behind their annual visit is hidden in their stomachs.