Whale shark (Rhincodon typus)
[Photo credit Peter Verhoog/Dutch Shark Society]
The whale shark is the largest living fish in the world and it is completely harmless ! These gentle giants filter feed on plankton, small crustaceans and very small fishes. Whale sharks can be found throughout the world’s temperate and tropical seas, with the exception of the Mediterranean. They grow up to 20 meters in length and can weigh in at a whopping 34 tons. Whale sharks are believed to live to over 100 years old. They may be docile, but that does not stop them travelling. These highly mobile animals can cover distances of up to 2000 km within two months.
The global population of whale sharks has declined by over 50% in the last 75 years and the whale shark was recently uplisted on the IUCN Red List to the Endangered status.
The whale shark has a flattened broad head and a blunt, almost square snout. Its top is a brownish grey with a white spot pattern between horizontal and vertical stripes that is unique to each individual. It belongs to the order of Orectolobiformes, or carpet sharks, making it closely related to the nurse shark. The whale shark is an oceanic species that occurs both offshore, as well as in coastal habitats. According to scientific observations, the abundance of whale sharks in the Dutch Caribbean is higher in the southern, leeward part of the islands, which is likely associated with seasonal upwelling-driven productivity that is known for the southeastern Caribbean area.
We know very little about the biology of whale sharks. They bear live young and are thought to produce a litter once every two years. Incidental records and data from animals in captivity suggest that they mature after somewhere between 9 and 30 years of age, and have a gestation period just under a year followed by a long resting period. It is believed that young whale sharks grow very quickly, after which the growth rapidly slows when they reach maturity. All this would explain the very few records pregnant females and very small whale sharks.
The global whale shark population has two subpopulations in the Indo-Pacific and Atlantic Ocean, where reductions of 63% and 30% are inferred respectively. Fisheries are the main cause of this, in addition to bycatch in nets, vessel strikes, and unregulated tourism in high aggregation sites. In the Caribbean, coastal development, cruise ship tourism, and land-based sources of pollution could pose a threat as well. Thankfully, targeted fisheries no longer exist in the Caribbean. However, because of the highly mobile nature of the species, it can easily swim into a zone where fisheries do pose a threat. Whale shark catches are often associated with tuna fisheries because tuna naturally tend to aggregate under objects, or near larger animals such as whale sharks. The international trade in whale shark is regulated under CITES*, but regional management and conservation is still warranted to supplement the protection of this truly emblematic species.Sources: IUCN Red List of Threatened Species Red List status: ENDANGERED SPAW Whale Shark: fact sheet