Whale Sharks (Rhincodon typus) are a rare and special sight on our tours. We see them a few times each year, and each encounter is special. Although they can grow quite large (40+ ft) their spots provide excellent camouflage. They are more frequent in the deep water of our Niihau boat tours than on our Napali Coast boat tours, although they are seen on both.
They are the true gentle giants of the sea. Despite the name, “shark”, they are non aggressive, non threatening, and their tiny remnant teeth are so small they feel like sand paper. They are curious creatures who will approach the boats as well as any swimmers we put in the water. Although it is not recommended to touch them (they have a protective membrane/slime that is believed to protect them from infections and parasites), they have been known to nudge snorkelers and divers as though they crave attention.
This gentle and slow filter feeding shark is the largest living fish species. A solitary creature, it is rarely seen in groups unless feeding at locations with an abundance of food. This distinctively-marked shark is believed to have originated about 60 million years ago.
The name “whale shark” comes from the fish’s large size and eating habits; that is, a shark as large as a whale that shares a similar filter feeder eating mode.
As a filter feeder it has an enormous mouth which can be up to 1.5 m (5 ft) wide and can contain up to 300 rows of tiny teeth. Two small eyes are located towards the front of the shark’s wide, flat head. The body is mostly grey with a white belly; three prominent ridges run along each side of the animal and the skin is marked with a “checkerboard” of pale yellow spots and stripes. These spots are unique to each whale shark and because of this can be used to identify and recognize individual animals. The shark has two pairs each of dorsal fins and pectoral fins. As a juvenile a whale shark’s tail has a larger upper fin than lower fin while the adult tail becomes more crescent-shaped. The largest Whale Shark specimen regarded as accurately recorded was 12.65 m (41.5 ft) long, weighed more than 21.5 tons (47,300 lb), and had a girth of 7 m (23 ft).
The Whale Shark feeds on phytoplankton, macro-algae, plankton, krill and small nektonic life, such as small squid or vertebrates. The many rows of tiny teeth play no role in feeding – instead the shark sucks in a mouthful of water, closes its mouth and expels the water through its gills, trapping anything larger than 2 to 3 mm in its sieve-like gill plates.
The life span of a Whale Shark is estimated to be between 60 and 150 years.
The Whale Shark is targeted by artisanal and commercial fisheries in several areas where they seasonally aggregate. The population is unknown and the species is considered vulnerable by the IUCN.
See Wikipedia, “Whale Shark”, http://en.wikipedia.org/wiki/Whale_shark