Classification
Kingdom: Animalia
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Lamniformes
Family: Cetorhinidae
T. N. Gill, 1862Genus:Cetorhinus
Blainville, 1816Species:C. maximus
Phylum: Chordata
Class: Chondrichthyes
Subclass: Elasmobranchii
Order: Lamniformes
Family: Cetorhinidae
T. N. Gill, 1862Genus:Cetorhinus
Blainville, 1816Species:C. maximus
Common Name.Basking shark
Morphology
Aside from their large size, Basking Sharks are characterised by their powerful lunate (or crescent-shaped) tail, very large mouth, pointed nose and five huge gill slits which almost encircle the head. Weighing up to 7 tonnes (average 4.5 tonnes), the maximum reported size of a Basking Shark is 12m, although the existence of specimens of 15.2m length has been suggested. However, most adults do not exceed 9.8m
summary? ( bilateral )
summary? ( bilateral )
Biology
. Despite their size, and visibility during summer months, researchers are only just beginning to piece together the life history of the Basking Shark; yet there remains much we don’t know about the largest shark in UK waters
. Basking Sharks appear quite social animals and are seen singly, in small groups or in schools of hundreds of individuals feeding in areas of high plankton concentration.
. There is little data on Basking Shark reproduction with only a single reported catch of a pregnant female carrying six pups reported in 1943. This leads to the theory that females give birth in areas of low or no fishing pressure, possibly segregating from the general population.
. Fisheries captures of Basking Sharks off the British Isles during the summer revealed that the individuals present were predominantly adult females, outnumbering males by as much as 40:1. However, the few individuals that were caught during winter months were mostly male.
. Basking Sharks appear quite social animals and are seen singly, in small groups or in schools of hundreds of individuals feeding in areas of high plankton concentration.
. There is little data on Basking Shark reproduction with only a single reported catch of a pregnant female carrying six pups reported in 1943. This leads to the theory that females give birth in areas of low or no fishing pressure, possibly segregating from the general population.
. Fisheries captures of Basking Sharks off the British Isles during the summer revealed that the individuals present were predominantly adult females, outnumbering males by as much as 40:1. However, the few individuals that were caught during winter months were mostly male.
Morphology
Aside from their large size, Basking Sharks are characterised by their powerful lunate (or crescent-shaped) tail, very large mouth, pointed nose and five huge gill slits which almost encircle the head. Weighing up to 7 tonnes (average 4.5 tonnes), the maximum reported size of a Basking Shark is 12m, although the existence of specimens of 15.2m length has been suggested. However, most adults do not exceed 9.8m.Other key identifying features are the strong lateral keels on the caudal peduncle (where the tail joins the body) the bristle-like gillrakers and rows of hundreds of minute teeth that fill the mouth. The mouth can be well over 1m wide in adult sharks. Basking Sharks also have huge livers that account for up to 25% of their body weight and provide the shark with near-neutral buoyancy.
Distribution Map
Importance: Ecological and Economical
Seen only at certain times of the year, Basking Sharks (Cetorhinus maximus) are hard to miss when they appear at the surface in coastal areas. The huge, sail-like dorsal fins of these enormous, ponderous-swimming sharks are readily visible from distances up to several miles (kilometres).
Traditionally, the seasonal appearance of Basking Sharks was a reliable time to harpoon these gigantic sharks for food, leather, and liver oil. Some of these fisheries also generated an unexpected ‘bonus’: a great deal of basic biological information about Baskers was collected. But centuries of concentrated harvesting off the shores of many countries have left Basking Shark populations much depleted. Entanglements in commercial fishing gear also took their toll of Basking Shark lives. The resultant economic loss was deemed so severe off British Columbia, Canada, that between 1955 and 1956 the bow of a government vessel was outfitted with a huge steel blade which was used to kill more than a hundred of the ‘problematic’ Baskers by neatly slicing them in two — up to 36 individual sharks a day were killed in this manner. In consequence of such commercial harvesting and eradication programs, few Baskers are seen each year in places where they were formerly abundantBasking sharks, Cetorhinus maximus (Gunnerus, 1765), are recognized by their huge sizes, conical snouts, sub-terminal mouthes, extremely large gill slits, dark bristle-like gill rakers inside the gills (present most of the year), strong caudal keels and large lunate (curved) tails. Basking sharks have numerous, small teeth
Traditionally, the seasonal appearance of Basking Sharks was a reliable time to harpoon these gigantic sharks for food, leather, and liver oil. Some of these fisheries also generated an unexpected ‘bonus’: a great deal of basic biological information about Baskers was collected. But centuries of concentrated harvesting off the shores of many countries have left Basking Shark populations much depleted. Entanglements in commercial fishing gear also took their toll of Basking Shark lives. The resultant economic loss was deemed so severe off British Columbia, Canada, that between 1955 and 1956 the bow of a government vessel was outfitted with a huge steel blade which was used to kill more than a hundred of the ‘problematic’ Baskers by neatly slicing them in two — up to 36 individual sharks a day were killed in this manner. In consequence of such commercial harvesting and eradication programs, few Baskers are seen each year in places where they were formerly abundantBasking sharks, Cetorhinus maximus (Gunnerus, 1765), are recognized by their huge sizes, conical snouts, sub-terminal mouthes, extremely large gill slits, dark bristle-like gill rakers inside the gills (present most of the year), strong caudal keels and large lunate (curved) tails. Basking sharks have numerous, small teeth
Interesting Facts
The basking shark (Cetorhinus maximus) got its common name from appearing to be basking on the ocean's surface while feeding. They can be found all over the world in temperate waters as low as 3,000 feet below the surface. The basking shark is the second largest shark in the ocean; the whale shark is the first. These sharks are usually between 20 feet to 26 feet in length and can weigh up to 4 tons, but the largest basking shark to ever be caught on record weighed in at about 19 tons and had a length of 40.3 feet. This occurred back in 1985 in the Bay of Fury located in Canada. Unfortunately, due to excessive fishing this shark does not get the chance to grow like it once used to. The basking shark and the great white shark look a great deal alike, but there are various easy ways to tell the two species apart. The basking shark has defined gill slits that look to go the whole way around the head of the shark, placoid scales cover the shark's textured skin, they have a pointed nose, smaller eyes, smaller teeth and usually a smaller girth. This shark's color may vary, but it is generally a dark brown/almost black or blue, which fades to a whitish color along the ventral area.
The basking shark is a filter feeder or suspension feeder; they get their nutrition by filtering zooplankton, small invertebrates and small fish. They can filter up to 2,000 tonnes of water an hour. The megamouth shark and whale shark are other filter feeders, but unlike the basking shark those two species can suck and pump water through their gills, while the basking shark just uses that water that is pushed into their gills as they are swimming.
The basking shark are aplacental viparious or ovoviviparious; the embryos receive nutrition first from the mother's yolk sac and then on the mother's ova because there is no placenta to transfer the nutrition from the mother's body to her young. Gestation is believed to take a little over a year, but it may take as many as three. They are born fully developed at about 5-6.5 feet in length, making them the largest shark pups out there. Sadly, the number of young is not certain and once they are born they have to fend for themselves. Their mothers do not partake in any maternal actions. Only one pregnant basking shark was believed to be caught. Mating is believed to take place in the late summer. Maturity is estimated to between a length of 4.6 meters and 6 meters.
The basking shark is a filter feeder or suspension feeder; they get their nutrition by filtering zooplankton, small invertebrates and small fish. They can filter up to 2,000 tonnes of water an hour. The megamouth shark and whale shark are other filter feeders, but unlike the basking shark those two species can suck and pump water through their gills, while the basking shark just uses that water that is pushed into their gills as they are swimming.
The basking shark are aplacental viparious or ovoviviparious; the embryos receive nutrition first from the mother's yolk sac and then on the mother's ova because there is no placenta to transfer the nutrition from the mother's body to her young. Gestation is believed to take a little over a year, but it may take as many as three. They are born fully developed at about 5-6.5 feet in length, making them the largest shark pups out there. Sadly, the number of young is not certain and once they are born they have to fend for themselves. Their mothers do not partake in any maternal actions. Only one pregnant basking shark was believed to be caught. Mating is believed to take place in the late summer. Maturity is estimated to between a length of 4.6 meters and 6 meters.
Vocabulary
1. Heterocercal ? the upper lobe is longer than the lower lobe
2. Demersel ? live primarily on the bottom
3. Ampullae of lorenzini ? jelly filled canals that can detect electrical and magnetic fields,used to help locate prey.
4. Viviparous ? live beares
5 Caudal ? is a tail
2. Demersel ? live primarily on the bottom
3. Ampullae of lorenzini ? jelly filled canals that can detect electrical and magnetic fields,used to help locate prey.
4. Viviparous ? live beares
5 Caudal ? is a tail