Whale Shark

ORDER: ORECTOLOBIFORMES
FAMILY: RHINCODONTIDAE
CLASS: CONDRICHTHYES
GENUS: RHINCODON

LENGTH: 12.2m
WEIGHT: 13.6 tonnes
LONGEVITY: Approximately 70 years
DIET: Plankton
SEXUAL MATURITY: About 30 years
GESTATION: Unknown
CALF SIZE: 40 – 60cm long
PROTECTION STATUS: Threatened

Whale sharks are regarded as the largest fish in the ocean. These slow moving filter feeding sharks grow up to 12m long and weigh up to 13.6 tonnes at full maturity. The whale shark is found in tropical waters and warm waters, living in the open sea with a life span of up to 70 years.

The species is believed to have originated about 60 million years ago. The name “whale shark” comes from the fish’s physiology – like a whale, it is both large and also a filter feeder. The shark was first identified in Table Bay, South Africa, in 1828.

The whale shark inhabits the world’s tropical waters. While believed to be pelagic, these creatures tend to congregate at several coastal sites around the globe, one of them being Pemba in Mozambique and the other, Zanzibar.
Although generally found deeper in the ocean, whale sharks often swim near the coastline, entering lagoons and coral atolls, as well as near estuaries and river mouths.

The shark’s range is generally restricted to about 30 degrees latitude. It is capable of diving to depths of as much as 700m. Although whale sharks are solitary animals, they are occasionally found congregating when feeding where there is an abundance of food.

The shark’s body, although used for swimming, is not conducive to swimming – somewhat unusual for a fish. Its top speed is around 5km per hour. As a filter feeder, the shark has a capacious mouth of up to 1.5m wide. It has up to 350 rows of tiny teeth that seem to serve no purpose – it uses its pair of five large gills to filter phytoplankton from the water into its stomach.

The whale shark’s skin is up to 10 cm thick and is covered in a “checkerboard” pattern of pale yellow spots and stripes. These patterns are unique to each individual whale shark and are used to identify an accurate population count through scientific research.

The whale shark is one of only three known filter feeding shark species. It feeds on phytoplankton, macro-algae, plankton, krill and small nektonic life, such as small squid or vertebrates. It sucks mouthfuls of water into its mouth and through its gills, where dermal denticles trap the micro-organisms. The water is expelled through the gills while anything larger than 3mm in diameter is trapped and swallowed.

The whale shark does not pose any threat or danger to humans. They are actually gentle giants and can be playful with people swimming or diving near them. If anything, divers and swimmers only risk being unintentionally struck by the shark’s large tail fin as it swims by.