Information on Basking Shark

Basking sharks (Cetorhinus maximus) are the world's second largest fish species after the whale shark (Rhincodon typus), and can grow up to 35m in length. Besides this, they are also one of the three filter feeding shark species on the planet, the other two being the whale shark (Rhincodon typus) and the Megamouth Shark (Megachasma pelagios). Basking sharks unlike the great white shark are docile creatures, therefore also known as 'gentle giants'. The term 'basking' means to bask in the sun is given to this shark species because of its habit to swim directly underneath the surface of the water. Basking sharks mostly swim together in a row in such a way that the dorsal and caudal (upper lobes) fins penetrate into the water. This swimming style imparts the impression of one mammoth animal which is why people named this shark as 'sea monster', despite them being harmless. The taxonomy of Basking sharks is as follows:

Kingdom: Animalia
Phylum: Chrordata
Class: Chondrichthyes
SubClass: Elasmobranchii
Order: Lamniformes
Family: Cetorhinidae
Genus: Cetorhinus
Species: Cetorhinus maximus

Appearance

Basking sharks are enormous cartilaginous sharks that can grow up to an average of 7-9 m in length, with an average weight of 8580 pounds. Sharks which are 11m long have also been reported. Their bodies are grayish brown in color with the bellies being a little paler. Their faces feature a large snout which ends into a rounded point. The mouth is so wide, with the edges stretched far across the face, thereby giving the shark an appearance like it's smiling. The size of the open mouth is huge with 100 tiny, rounded teeth. Long gill slits are present surrounding the head, which are the most distinguishable features of this animal. Basking sharks have a large triangular first dorsal fin and smaller (half the size of first dorsal fin) second dorsal fin and anal fins. They have a huge liver (making 25% of body weight) which provides them with neutral buoyancy.

Distribution and Habitat

Basking sharks are highly migrating species and keep emerging and disappearing from different areas. This behavior has left scientists mystified. They are mostly found off the coast of Northern Ireland and United Kingdom. Basking sharks prefer temperate oceans and thus found in the western Mediterranean sea and western Atlantic. They are not found in the tropics, and if at all they are found, then it's usually the dead or stranded bodies. During spring and winter, they are found off California's coast. Usually basking sharks are found wherever the plankton level is high. In winter, they are seen to migrate from shallow to deeper waters, however, the exact pattern of these animals, their migratory behavior, etc are yet to be understood clearly.

Feeding Behavior

Basking sharks are found feeding near the surface of the water. Their cavernous mouth can open 1.2 m wide and are observed to swim with their mouth wide open. The open mouth allows the water to pass through the distended comb like gill rakers. Prey from the water get entangled in the gill rakers (act like filters), which are further ingested by the shark by the closing movement of its mouth. Basking sharks feed entirely by swimming through water with their open mouth and do not suck in the water for filtering. This feature makes them different from the other two filter feeding species. Their platter of prey items comprises barnacles, fish eggs, tiny copepods, deep water oceanic shrimp and decapod larvae.

Reproduction

The information available on the reproductive behavior of basking sharks is limited. The sizes at which the male and female sharks mature have not been confirmed. However, speculations are that females mature when they reach 8m in length and males, when they reach 5m in length. A single catch of a pregnant female shark carrying six pups was reported, which suggested the theory that females give birth to their young ones in the areas of no or low fishing pressure. Basking sharks are believed to be ovoviviparous. This means that the fertilized eggs are developed in the womb of the female shark with no gain of additional nutrition from the mother shark until they are born as young pups. The gestation period is believed to 14 months. The pups exhibit interuterine cannibalism and when born are larger than other sharks.

Swimming and Breaching Behavior

Basking sharks are slow swimmers and ordinarily cruise at around 2.5 to 4 mph. They swim by moving their bodies from side to side and not just their tails as done by the other sharks. However, appearances can be deceptive! This shark may seem cumbersome and slow moving, however, they also exhibit breaching behavior. Breaching involves the sudden eruption of the shark from the water into the air, rolling in mid air and then crashing into the water. The shark may perform this somersault 3-4 times (30sec each ) in a row. The exact reason for this behavior is unknown. This can prove dangerous to boats in the vicinity as they are in danger of capsizing.

Basking sharks were initially hunted for their liver that is high in vitamin A content and oil. The liver was sold as an aphrodisiac in Japan and the oil was used as lamp oil, as well as in the manufacture of cosmetics. Their fins are in great demand in the far east, where it is used to prepare fin soup. Accidental catch by the fishery industry, low reproductive rates, long gestation period and long growth rate have got basking sharks listed on the IUCN list of endangered shark species. Basking sharks are less aggressive and harmless to man. However, be on the look out as you don't want to be in a small boat near the animal when it's breaching!