Whale Sharks , Rhincodon typus, can reach a length of 13 meters and a weight of more than 21.5 tonnes. It is the sole member of the genus Rhincodon and the family, Rhincodontidae, which belongs to the subclass Elasmobranchii in the classChondrichthyes. The species originated approximately 60 million years ago.
Its range is generally restricted to about ±30° latitude. It is capable of diving to depths of at least 1,286 meters and is migratory.Dive-Careers.com conduct instructor training programmes in both Bohol and El Nido, Palawan, Philippines as well as Koh Tao, Thailand. Just like I am travelling around from instructor development course to IDC, there is evidence to suggest the same group of whale sharks migrates throughout Asia. This highlights the importance of an international effort to help with whale shark protection
During our Sierra Madre/Infinite Blue IDCs (PADI Dive Instructor courses) on Bohol, Philippines , Dr. Alessandro Ponzo conducts a seminar for us on the research his organisation, Large Marine Vertebrates, is conducting on whale sharks in the Philippines. Dr Ponzo has set up research stations in both Oslob and Leite to further investigate the impact tourism is having on whale shark populations. He presents a fascinating seminar packed with wonderful information about the little understood life cycle and behaviour of whale sharks. From Dr Ponzos seminar we get a strong appreciation for the imminent danger whale sharks face through short term exploitation. Dr Ponzo points out that in 1997, the last year of legal whale shark fishing in the Bohol Sea, 700 Whale sharks were fished. The population at present in the Philippines stands at around 350 sharks. With a return to uncontrolled fishing in Philippines, we could see the total annihilation of Philippine whale shark populations in less than a year.
The Philippine whale shark population also faces the threat of unregulated tourism in such areas as Oslob where whale shark feeding is used to attract large numbers of tourists. Whale Sharks feed on macro-algae, plankton, krill, and small vertebrates. They also feed on small fish and the clouds of eggs and sperm during mass spawning of fish shoals. The many rows of vestigial teeth play no role in feeding. Feeding occurs either by ram filtration, in which the animal opens its mouth and swims forward, pushing water and food into the mouth, as highlighted by the movements of the sharks around around divers at such dive sites like Chumporn Pinnacle off Koh Tao, Thailand, or by active suction feeding, in which the animal opens and closes its mouth, sucking in volumes of water that are then expelled through the gills. In both cases, the filter pads serve to separate food from water.
Whale sharks migrate to feed and possibly to breed. Feeding by locals in such areas as Oslob, where the fisherman are catching krill to keep whale sharks in the local area and draw tourists, are clearly affecting eating patterns and migratory routes. Our whale shark seminar during the Sierra Madre IDCs, Bohol, Philippines are aimed at highlighting this problem and encouraging our IDC candidates to participate as volunteers on the research programmes Dr Ponzo is running at both Oslob and Leite. Jaki and Brett from Sierra Madre / Infiinte Blue Divers are actively campaigning on Bohol against supporting such areas as Oslob with dive tourism. Sadly many dive centers continue to send divers for this orchestrated and harmful whale shark experience.
Neither mating nor pupping of whale sharks has ever been observed.
The capture of a female pregnant with 300 pups indicates that whale sharks are ovo-viviparous. The eggs remain in the body and the females give birth to live young which are 40 to 60 centimetres long. There is evidence that the pups are not all born at once, but rather that the female retains sperm from one mating and produces a steady stream of pups over a prolonged period. It is believed that they reach sexual maturity at around 30 years and the life span is an estimated 70 to 100 years. This long life span, late sexual maturity and relatively low birth rates make whale shark conservation difficult.
In 2009 at Pilar, Philippines, marine scientists discovered what is believed to be the smallest living specimen of the whale shark. The young shark measured only 38 centimetres. Recently, similar sized specimens were found off the coast of India. Little is known about the early life cycle of whale sharks. It is believed that they disappear into the great ocean depths until they reach adolescence. The spotted markings of a whale shark are useful for camouflage of a bottom dweller, similar to a carpet shark, so, it is assumed these markings are important to the protection of young whale sharks dwelling on the bottom at great depths.
Koh Tao. Thailand remains a very popular destination to see adolescent whale sharks. There are frequent sightings of whale sharks in March to April and again September to October, with occasional sightings throughout the year. It remains one of the best chances of diving with whale sharks of any dive destination in Asia. Popular dive destinations need strict codes of behaviour defining diver interactions with the marine environment. During our Divemaster and Instructor Progammes with Buddha View PADI IDC Resort on Koh Tao, we conduct a Marine Resource Management seminar helping dive professionals develop knowledge about the marine environment and a code of practice to impart to their future divers. We encourage the following general guidelines, promoted by The Shark Trust, the Australian Department of Conservation and Land Management, and PADI Project AWARE Foundation be followed for both their own safety and for the safety of the sharks.
Code of Conduct for Swimmers and Divers
- Do not attempt to touch, ride, or chase a whale shark
- Do not restrict normal movement or behavior of the shark
- Maintain a minimum distance of 3 meters from the head and 4 meters from the tail (caudal fin) of the whale shark
- No flash photography
- Do not use diver propulsion vehicles near a whale shark
In 1998, the Philippines banned all fishing, selling, importing and exporting of whale sharks for commercial purposes, then Thailand in 2000, followed by India in May 2001, and Taiwan in May 2007. They are currently listed as a vulnerable species; however, they continue to be hunted in parts of Asia, such as Taiwan and the Philippines. The population numbers are unknown and the species is considered vulnerable by the IUCN. It is listed, along with 6 other species of shark, under the CMS Memorandum of Understanding (MoU) on the Conservation of Migratory Sharks.
As dive professionals we are in a unique position to highlight, through education, the plight of whale sharks and the importance of their conservation to the general public. We hope through our Marine Resource Management seminars at our IDC and divemaster programmes throughout Asia and promoting such research projects and volunteer work as that done by Large Marine Vertebrates in the Philippines, we are making, if only small, at least a positive change to the perception of our marine environment and an appreciation for the continued existence of whale sharks.