Rhincodon typus

Whale Shark

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Whale Shark

 

Description

The whale shark is the largest fish in the world; with its vast size it resembles the whales from which its common name is derived. The head is flattened and the wide mouth, positioned at the tip of the snout, stretches almost as wide as the body. The dorsal fin is particularly large and the tail has a half-moon shape. The patterning of the body is very distinctive with its dark greyish-blue colour on the back and sides, and array of pale yellow blotches; the undersurface is pale. Stout ridges travel the length of the body, ending at the tail shaft. Five massive gill slits occur on the side of the head and within these there is a sieve like structure of cartilage. Curiously, the mouth contains around 300 tiny teeth although the function of these is unknown.

Geography

Whale sharks, Rhincodon typus, are generally found between latitudes of 30 degrees N and 35 degrees S. Whale sharks congregate throughout the year at several different areas that provide prime feeding opportunities. These areas include Ningaloo Reef off of western Australia in March and April, the Belize Barrier Reef in April and May, and off of North Island, New Zealand from November to April. This species also gathers in the Sea of Cortez but with no seasonal regularity.

Ecosystem

Whale sharks prefer oceans of water temperatures between 21 and 25 degrees Celsius where upwelling occurs. This species is found at many depths within open ocean and has been found as deep as 2000 to 3000 m near the Galapagos Islands. Whale sharks may also have a small layer of fat, helping them to survive the cold temperatures when they make a deeper dive (Graham 2006).

Range depth: 0 to 2000 to 3000 m.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: pelagic ; reef

Conservation

The Whale Shark (Rhincodon typus) is a cosmopolitan tropical and warm temperate species and is the world's largest living chondrichthyan. Its life history is poorly understood, but it is known to be highly fecund and to migrate extremely large distances. Populations appear to have been depleted by harpoon fisheries in Southeast Asia and perhaps incidental capture in other fisheries. High value in international trade, a K-selected life history, highly migratory nature and normally low abundance make this species vulnerable to commercial fishing. Dive tourism involving this species has recently developed in a number of locations around the world, demonstrating that it is far more valuable alive than fished.

 

Threats

Major Threats
Small-scale harpoon and entanglement fisheries have taken place in various regions of the world, including India (whale shark fishing banned in 2001), Pakistan, Taiwan (Province of China), the Philippines (banned in 1998) and the Maldives (prior to protection in 1995). These took Whale Sharks primarily for their meat, liver oil, and/or fins (Compagno 1984a, Ramachandran and Sankar 1990, Trono 1996, Hanfee 2001, Alava et al. 2002). Liver oil was traditionally used for water-proofing boat hulls. The huge fins are low quality but of high value as restaurant "signboards" in east Asia, and the soft meat (known as "tofu shark") is in great demand in Taiwan (Province of China).

Fishermen in the Maldives used to take 20-30 Whale Sharks per year for their oil, but reported declining catches during the 1980s to early 1990s (Fowler 2000). In a study in the Philippines, it was found that in 1997 there was a 29% decline in the whale shark catch at two of the primary sites, despite an increase in effort due to rising prices for exported products (Alava et al. 2002). The increased fishing effort and falling catches led to the 1998 fishery ban, although illegal fishing and attempted export of meat still continues on a small scale, with shipments having been impounded by customs authorities (Anon 2002b).

In Pakistan, the flesh was traditionally eaten either fresh or salted, and liver oil used for treating boats (Compagno 1984a). The number of sharks taken each year was small and often accidental bycatch (Silas 1986, Seshagiri Rao 1992). Recent landings are unknown.

A traditional small-scale seasonal harpoon fishery in India took whale sharks for their liver oil (Prater 1941, Rao 1986, Silas 1986, Vivekanandan and Zala 1994). About 40 were harpooned during April 1982 (Silas 1986), but demand for "tofu shark" meat in Taiwan (Province of China) led to increased fishing effort in Gujarat during the 1990s (Hanfee 2001). Prices rose significantly after 1997, with 279 Whale Sharks taken in January?May 1999. One hundred and forty-five sharks were taken offshore (10-15 km) in December 1999, and 160 in coastal waters in January?May 2000. The fishery closed in May 2001, when the Indian Ministry of Environment and Forests legally protected whale sharks in territorial waters.

Whale Sharks have been targeted for many decades in Taiwan (Province of China), but catches appear to have declined since the 1980s (Chen et al. 1996, Joung et al. 1996). Billfish harpooners from Hengchun Harbour, fishing south of Penghu, reportedly landed 50-60 Whale Sharks each spring in the mid-1980s, but annual landings at this location subsequently declined to about 10 sharks, and fewer still in 1994 and 1995. In 1995, landings throughout Taiwan (Province of China) were approximately 250-272, around 158 taken as bycatch in set nets, 114 by harpoon (Chen et al. 1996). The government introduced a Whale Shark reporting system in 2001. This and other sources indicate that the total number of Whale Sharks caught during 2001 was 89 (38 by set nets, 36 in the billfish harpoon fishery and 15 by other methods), and that 94 sharks weighing about 104 t in total were landed during the 12 months from March 2001 to March 2002 (Anon 2002b, Chen and Phipps 2002). The domestic catch has apparently declined by 60-70% since surveyed by Chen et al. (1996). Chen and Phipps (2002) note that the sum of the reported catch and imports is smaller than the quantity of Whale Shark meat on the domestic market, indicating that official data under-represent imports.

Wholesale Whale Shark meat prices in Chinese Taipei peaked at US$7.00/kg in the late 1990s (Liu et al. 2002) when a 10 t shark was worth approximately US$70,000, subsequently falling to US$2.00/kg in 2001 (Chen and Phipps 2002).

Although Ramachandran and Sankar (1990) considered that R. typus was an underexploited species, there are now concerns that Whale Shark populations are decreasing in many locations as a result of stock depletion by unregulated fisheries (Anon 2002b). Ecotourism industries based on viewing Whale Sharks are now developing in several locations, including Mexico, Australia, Philippines, south-eastern Africa, Seychelles, Maldives, Belize and Honduras (Norman 1999, Anon 2002b, Newman et al. 2002). The number of people swimming with Whale Sharks at Ningaloo Reef, Western Australia, during the short whale shark season from March to June, increased from 1,000 in 1993 to almost 5,000 in 2002 (Colman pers. obs. 1997). This well-managed industry contributes significantly to the national and regional economy (overseas participants make up 65-75% of participating tourists).

Ecotourism has taken over from hunting as a significant source of income for Maldivian operators, since the small fishery that once existed ceased after legislation was introduced in 1995 to protect whale sharks (C. Anderson pers. comm.). Similarly, the development of an important whale shark ecotourism industry in areas of the Philippines that experience large seasonal aggregations of whale sharks is now underway (Anon 2002b).

In the Seychelles, 162 tourists/week interacted with R. typus in November 1996 and the industry could be worth US$3?5 million annually there (Newman et al. 2002). Revenues are also significant in several other range states, indeed rather higher than revenues from fisheries for this species (Anon 2002b). To ensure that high levels of tourism do not have an adverse effect on the behaviour of Whale Sharks at these locations and other aggregation sites identified in future, monitoring must continue as a priority.

In Tanzania Whale Shark sightings are apparently on the increase. Surprisingly, fishermen do not actively hunt whale sharks and do not consume the meat; nor do they recognise that the fins may have any value. Four individuals caught in March 2001 were not consumed nor were their fins sold. A very small amount of meat was taken, possibly for medicinal purposes (S. Yahya and N. Jiddawi pers. comm.). They are avoided by net fishermen because of potential damage to the nets. Whale sharks have been sighted for the last few years during the inter-monsoonal period of March-June off Zanzibar. They are caught in purse, drift and gillnet fisheries.

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