Rhincodon typus
Basking shark
(Also: Tofu sa; Tofu shark; Whale shark; Whale-shark; Whaleshark)

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. (Clark, 1992; Duffy, 2002; Eckert and Stewart, 2001; Gunn, et al., 1999; Heyman, et al., 2001)

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). ("Whale Shark (Rhincodon typus) Recovery Plan Issues Paper", 2005; Colman, 1997; Graham, et al., 2006)

Whale sharks are the largest known species of fish, with the largest specimen on record measuring 20 m in length and weighing 30,8044 kg. On average, members of this species are 7 m in length. Whale sharks have a large rounded mouth and eyes located on the sides of their broad head. They have two dorsal fins, one large and one small, a pair of pelvic fins, and a pair of pectoral fins to help them steer in water. Above their pectoral fins are 3 ridges on each side, one of which extending to their tail. Whale sharks are white on the ventral side, and the dorsal side is pale blue to gray with lighter smaller spots before the pectoral fins and stripes with larger spots extending to their spotted tail. Each shark has a distinct pattern of white spots and stripes and can be identified by humans from photographs by using an astronomy based algorithm. Although they are born without any distinguishing features, once the spots and stripes are present they do not change. (Arzoumanian, et al., 2005; "Whale Shark (Rhincodon typus) Recovery Plan Issues Paper", 2005; Clark, 1992; Colman, 1997; Graham and Roberts, 2007)

Growth of the vertebral rings in whale sharks is rapid during the first few years of life, and growth has slowed by 20 years of age. Information regarding the growth and development of whale sharks is largely unknown. Data gathered regarding growth in captivity is considered unrepresentative of growth in the wild, as space requirements for optimum growth are unknown. (Norman and Stevens, 2007)

Little information is available regarding the mating systems of whale sharks. Like many other species of sharks, whale sharks have two reproductive extensions called claspers between two pelvic fins. These claspers assist with holding onto the female and transferring sperm successfully. In a study by Schmidt et al. (2010), 29 of 304 embryos from a harpooned female whale shark were retained for DNA analysis to determine paternity. From this 10% litter sample, Schmidt et al. concluded all 304 embroys had the same father. Embryos from this shark were also at varying developmental stages, suggesting that whale sharks may be capable of delayed fertilization. (Colman, 1997; Norman and Stevens, 2007; Schmidt, et al., 2010)

Whale sharks are ovoviviparous, though little information is otherwise known regarding reproduction of whale sharks. Males are thought to reach sexual maturity when 30 years of age and at least 9 meters in length. Age of sexual maturity in females is unknown. In 1995, a female whale shark harpooned in Taiwan was found carrying 304 embryos. Only 15 of these were alive when their mother was recovered, and only one survived for 143 days in captivity. (Colman, 1997; Norman and Stevens, 2007; Schmidt, et al., 2010)

Currently very little is known about parental involvement of whale sharks. Reports of adults swimming with some younger whale sharks may suggest some measure of parental investment. It is also possible that younger whale sharks remain near adults for protection. (Martin, 2007)

It is estimated that whale sharks may live at least 100 years in the wild. It has been suggested that the number of growth rings on a whale shark's vertebrae may be an indicator of age. In captivity, whale sharks have lived anywhere from a handful of days to 8 years or longer. (Martin, 2007; Stevens, 2007)

Little is known about the behavior of whale sharks. They have been observed alone and also in groups of 100 or more individuals. Whale sharks have also been observed with other groupings of fish and manta rays. (Colman, 1997)

The home range of whale sharks is currently unknown.

It is thought that whale shark depend on their eyesight to recognize markings on other sharks. Their senses are likely similar to those of nurse sharks, which can "smell" chemicals in the water. Because they dive upon the approach of motorized boats and have large inner ears, whale sharks may also be able to detect low-frequency sounds. (Colman, 1997; Martin, 2007)

Whale sharks are one of only three known species of filter feeding sharks. Whale sharks feed by sucking water into their mouth, which also draws in plankton as well as jellyfish, anchovies, fish larvae, and coral. Once in the shark's mouth, the mix is pushed through a filter in the gills so that water leaves but prey remains. If something too large gets caught in its gills, a shark will sometimes cough to help clear the obstruction. Whale sharks have also been observed swimming through large gatherings of zooplankton and can easily decimate an entire school of krill in one pass. While it is currently unknown how much a whale shark eats in a day, they are thought to spend the majority of their day eating. Whale sharks gather along the Ningaloo Reef off of western Australia in March and April and along the Belize Barrier Reef in April and May, which is likely associated with spawning of coral and fish that occurs in these locations around the same time. Whale sharks also gather in New Zealand when the upwelling that occurs off North Island is at its weakest. This upwelling causes an abundance of nutrients for plankton which in turn attract larger animals that eat the plankton. (Clark, 1992; Colman, 1997; Gunn, et al., 1999; Heyman, et al., 2001; Stevens, 2007)

There are few known predators of whale sharks besides humans. Remnants of young whale sharks, however, have been found in blue sharks, blue marlin and killer whales. ("Whale Shark (Rhincodon typus) Recovery Plan Issues Paper", 2005)

Copepods, specifically Pandarus rhincodonicus, often live on the lips and fins of whale sharks, feeding on bacteria and other micro-organisms found on the skin. Because the mouth of copepods can move back and forth, they can also rid sharks of any irregularities found on the skin. Occasionally whale sharks are hosts to remora. (Norman, et al., 2000)

Use of whale sharks is common in eastern countries. In Taiwan, they are a popular source of food, though very expensive. Their flesh is high in water content and has a texture similar to tofu. As of 1997, only two fisheries in Taiwan harvested around 100 sharks each year. In India, when whale sharks are caught by fisheries, they are sometimes used as a source of food. Additionally, their liver contains oil used for waterproofing, shoe polish and to treat some skin diseases. Occasionally whale sharks are accidentally caught in fishing equipment and are sold to aquaria around the world. Whale sharks are currently banned from commercial fishing in Belize, Honduras, Maldives, Philippines, Thailand, India, Mexico, the United States, and Australia. ("Whale Shark (Rhincodon typus) Recovery Plan Issues Paper", 2005; Colman, 1997; Davis, et al., 1997; Quiros, 2005)

Whale sharks are also a source of ecotourism in areas like Australia and Belize. In Australia's Ningaloo Reef, the best time to scuba dive with the whale shark is between March and May. To avoid crowding a shark, some boat operators will only allow a small number of people in the water at a time. In Belize the best time to dive with whale sharks is between March and June. Because there are few regulations associated with whale shark ecotourism, as many as 80 divers will crowd a single shark. ("Whale Shark (Rhincodon typus) Recovery Plan Issues Paper", 2005; Davis, et al., 1997; Quiros, 2005)

Occasionally whale sharks damage fishing equipment when entangled. (Colman, 1997)

Because population data are currently unknown, it is difficult for agencies to determine whether whale sharks are at risk. The IUCN Red List considers whale sharks vulnerable and their populations to be decreasing. Whale sharks are also listed in Appendix II by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), meaning whale sharks potentially will need protection in the future. Fishing bans in many countries have been instated to help conserve this species. Efforts are also being made to educate fisherman, demonstrating that whale sharks are more valuable alive due to ecotourism and less valuable as a food source because of their slow rates of reproduction. Despite these efforts, poaching also still occurs, and many catches are simply not being reported. Other factors contributing to their conservation status include increased boat traffic (due to the sound and potential for being struck), damage to coral reefs, pollution, and global climate change. ("Whale Shark (Rhincodon typus) Recovery Plan Issues Paper", 2005; Chen and Phipps, 2002; Colman, 1997)