Fish Facts » Basking Shark
Description
The basking shark is one of the most recognizable of all sharks. Its massiveness, extended gill slits that nearly encircle the head and lunate caudal fin together help distinguish it from all other species. It possesses a conical snout and numerous large gill rakers modified for filter feeding. Its enormous mouth extends past the small eyes and contains many small, hooked teeth. The basking shark has a very large liver that accounts for up to 25% of its body weight. The liver is high in squalene, a low-density hydrocarbon that helps give the shark near-neutral buoyancy. Dorsal surface is typically grayish-brown but can range from dark gray to almost black. Ventral surface may be of the same color, slightly paler or nearly white.
Habitat
The basking shark is typically seen swimming slowly at the surface, mouth agape in open water near shore. This species is known to enter bays and estuaries as well as venturing offshore. Basking sharks are often seen traveling in pairs and in larger schools of up to a 100 or more. Its common name comes from its habit of 'sunning' itself at the surface, back awash with its first dorsal fin fully exposed.
Diet
Along with the whale shark and the megamouth shark (Megachasma pelagios), the basking shark is one of three species of large, filter-feeding sharks. However, the basking shark is the only one that relies solely on the passive flow of water through its pharynx by swimming. The basking shark is usually seen swimming with its mouth wide open, taking in a continuous flow of water. The whale shark and megamouth shark assist the process by suction or actively pumping water into their pharynxes. Food is strained from the water by gill rakers located in the gill slits. The basking shark's gill rakers can strain up to 2000 tons of water per hour. These sharks feed along areas that contain high densities of large zooplankton (i.e., small crustaceans, invertebrate larvae, and fish eggs and larvae). There is a theory that the basking shark feeds on the surface when plankton is abundant, then sheds its gill rakers and hibernates in deeper water during winter. Alternatively, it has been suggested that the basking shark turns to benthic (near bottom) feeding when it loses its gill rakers. It is not known how often it sheds these gill rakers or how rapidly they are replaced.
Fishery
In the past, basking sharks were hunted worldwide for their oil, meat, fins, and vitamin rich livers. Today, most fishing has ceased except in China and Japan. The fins are sold as the base ingredient for shark fin soup. A "wet" or fresh pair of fins can fetch up to $1,000 in Asian fish markets while dried-processed fins generally sell for $350 per pound. The liver is sold in Japan as an aphrodisiac, a health food, and its oil as a lubricant for cosmetics. From a 4-ton (3629 kg), 27 feet (8.2 m) basking shark, a fisherman will get 1 ton of meat and 100 gallons (380 liters) of oil.
Size
Second only to the whale shark (Rhincodon typus) in size, the basking shark can reach lengths up to 40 feet (12 m). The average adult length is 22-29 feet (6.7-8.8 m). Size at birth is believed to be between 5-6 feet (1.5-1.8 m). The basking shark is an extremely slow-growing species and may grow to 16-20 feet (5-6 m) before becoming mature.
Range
The basking shark is a coastal-pelagic species found throughout the world's arctic and temperate waters. In the western Atlantic, it ranges from Newfoundland to Florida and southern Brazil to Argentina and from Iceland and Norway to Senegal, including the parts of the Mediterranean in the eastern Atlantic. It is found off Japan, China and the Koreas as well as western and southern Australia and the coastlines of New Zealand in the western Pacific and from the Gulf of Alaska to the Gulf of California and from Ecuador to Chile in the eastern Pacific.
Source(s)
Florida Museum of Natural History
Source(s) on the web
http://www.flmnh.ufl.edu/fish/Gallery/Descript/baskingshark/baskingshark.html