- Sharks have roamed our seas for more than 400 million years, which means they inhabited the earth for nearly 200 million years before dinosaurs.
- Sharks are fish with skeletons made of cartilage instead of bone, but sharks’ slow growth and late maturity mean they have more in common with sea turtles and marine mammals than bony fish such as flounder or tuna.
- Sharks are a remarkably diverse group of fish. They range from less than a metre to 20 metres in length; they are found in most coastal regions but also in the deep ocean and even in fresh water. Some sharks lay eggs, but most give birth to live young. Most are top predators while a few feed on plankton. Sharks in turn are preyed upon by other sharks and sometimes killer whales.
- The term ‘shark’ often refers not only to shark species but also to the closely related rays and skates, as well as the oft-overlooked chimaeras (rat, rabbit and elephant fish).Collectively these cartilaginous species are known as chondrichthyan fish (forming Class Chondrichthyes).
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Sharks and rays do not have true bones like other fishes. They have cartilage instead which is lighter and much more elastic and allows them to bend in very tight circles.
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Sharks do not have swim bladders. A swim bladder is a gas filled sack inside the body of bony fishes that allows them to stay still without sinking. Sharks compensate by having a very big liver that is filled with oil. Even so, sharks sink unless they keep swimming forward. The exception is the Sandtiger Shark which swallows air to make itself more buoyant.
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A shark’s upper jaw is not fused to its skull like most animals. When a shark bites a large object, it is able to move its upper and lower jaw forward in order to take a bigger bite.
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Unlike other fishes, sharks are able to replace their teeth constantly. New teeth grow from the inner surface of the jaw and rotate forward when the old teeth get worn out or lost during feeding.
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Sharks and rays do not reproduce like other fishes. Most fish release clouds of sperm and eggs into the water column where they mix together. The fertilized eggs then float around until the fish larvae hatch and form schools of tiny fish. Male sharks have two organs called claspers attached to their anal fins. They insert one of these into the female shark’s cloaca (the entrance to the uterus) to transfer sperm (just like in mammals). Some sharks and rays incubate the eggs in their uteruses until the baby sharks are ready to be born. Other sharks and rays (i.e. skates) lay eggs and attach them to the reef.
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Sharks have between 5 and 7 gill slits on each side of their body in front of their pectoral fins. Bony fishes only have one pair. Having many exposed gill slits probably helps transfer more oxygen into their blood faster which allows them to swim very fast when they need to.
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Most shark’s skin is covered in small denticles instead of scales. Denticles are a lot like teeth. They have dentine in the centre and enamel on the surface. This makes shark’s skin very tough and abrasive like sandpaper. The shape and position of some shark’s denticles also helps reduce friction so that they can slip through the water easier.
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Sharks have an extra sense that is able to detect tiny electric fields. They can use this to find food that is buried or to search for animals to eat in the dark or in turbid water.
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Sharks and rays make up the sub-class of fishes called elasmobranches. This sub-class is part of a class of cartilaginous fishes called Chondrichthyes which also includes chimaeras (ratfishes).
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Over 100 million sharks are killed annually. Partly because of their fins for shark fish fin soup, as bycatch in up to 40 miles long drift nets of enormous fishing fleets, for medically completely ineffective cartilage powder or by the destruction of their habitats.
You will find shark products often at unexpected places as in restaurants, snack bars or supermarkets. Shark meat is offered also under various other names as Smoked Rock Salmon, Smoked Dogfish, a component of Fish & Chips or Imitation Crab Meat (Surimi). Also the worldwide protected and extremely threatened whale shark is on the Asian market (mainly Taiwan and Japan) still offered as Tofu Shark.
Besides the British the Germans consume most spiny dogfish. They produce the so-called “Schillerlocken” out of the sharks belly. The British use the spiny dogfish for “Fish & Chips “. This kind of shark is strongly overfished and its existence in the Northeast Atlantic decreased in the last 40 years by 90 percent.
Principal customers for shark fins are mainly eastern cultures in which shark fin soup represents a cultural meal. It is a remarkable fact that a shark fin, which consists to 90% out of cartilage, is extensively tasteless and only after days of boiling up in a broth becomes soft and gets the taste of the broth. Today shark fin soup is a status symbol because of the strongly risen prices within the last few years.
We can find shark products also in dog fodder, fish flour and even in fertilizers. From shark skin leather products such as purses, shoes or clock bracelets are produced.
Shark liver oil is frequently a component of the well-known cod-liver oil. In the health sector shark cartilage powders is marketed as fit making food additive although shark cartilages contains absolutely no fit making or other wholesome ingredients.
Most problematic is the marketing of shark cartilage as an anti-cancer means. The publication “Cancer Research” published in December 2004 confirms that shark cartilage preparations showed absolutely no effect against cancer.
However in the gel sector (food/pharmacy) shark collagen has few market chances although particularly Spain tries to penetrate into the market with shark collagen. Spain, one of the world largest shark fin producer, has 2002 forbidden to bring only the fins of sharks ashore. According to law the whole shark bodies must be brought now ashore. This leads now ridiculous-proves to the fact that out of the bodies the completely ineffective cartilage powder is made perforce.
In the cosmetics sector from shark cartilage won collagen is used for anti-fold creams and other preparations. Collagen from sharks is free of BSE and more kosher which makes it interesting for the Arab and Israeli markets.
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