Deep Blue Utila
click to enlargeThe whale shark, Rhincodon typus, is a filter feeding shark that is the largest living fish species. It can grow up to over 12 meters (40 ft.) in length. This distinctively marked shark is the only member of its genus Rhincodon and of its family Rhincodontidae (called Rhinodontes before 1984). It is grouped into the subclass Elasmobranchii in the class Chondrichthyes. An exact lifespan is unknown; there have been estimates of between 70 and 150 years.

Distribution and Habitat

The whale shark inhabits the world's tropic and temperate oceans. It is mainly pelagic (lives in the open ocean). In some area such as Utila it comes close in to feed. Dr Eric Hoffmayer has recorded a whale shark at 6,325 feet in depth, that is a distance of 1.198 miles down.

Anatomy and Appearance

The whale shark has a huge mouth and is a filter feeder, this contains around 300 rows of tiny teeth with 5 pairs of gills. Its body coloring can vary from a brownish to a dark gray / blue with a white belly, it also has 3 prominent dorsal ridges that run down each side.

click to enlargeThe whale shark is covered in lighter color spots, and these spots are unique to each whale shark and are used in the identification of whale sharks through the Ecocean photo ID library.

Its skin can be up to 5 inches thick, it also has two dorsal fins, two pectoral fins, two pelvic fins and one anal fin, its tail has a larger upper fin. The whale shark has a spiracle.

Diet

The whale shark is a filter feeder, there are only 3 filter feeding sharks that are known, apart from the whale shark there is the basking shark and the megamouth shark, it feeds mainly on plankton. As far as we know the teeth play no part in feeding.

Reproduction

click to enlarge We know very little about the reproduction of whale sharks, none have ever been seen mating or giving birth in 1956 a single egg was found off the coast of Mexico leading the world to believe the whale shark was oviparous but the capture of a pregnant female in July 1996 off the coast of Taiwan which was pregnant revealed 300 near term pups inside and indicated that they are in fact ovoviviparous.

It is not known when they become sexually mature, it is believed to be between 25 and 30 years old.

On March 7, 2009, in the Philippines they discovered the smallest living specimen of the whale shark it measured 15 inches (38 centimeters) in length.

Conservation

The whale shark is targeted by some commercial fisheries in several areas where they seasonally aggregate. The population numbers are unknown and the species is considered venerable by the IUCN .


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