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Pictures Great white shark dorsal fins breaking surface near Seal Island, False Bay, Geyser Rock and Dyer Island.Great White Shark Dorsal Fin
Shortly before sunset we were sailing with our boat close to Seal Island in the False Bay. There is a large seal colony on this island. Some fish bait hangs on a small red buoy, which is held into the water from the boat. A great white shark has followed the trail of the scent and has reached our boat. The dorsal fin can be seen quite distinctively. It is an individual, special feature of recognition of the shark, unique and unmistakable.
Following the article, which appeared in the edition of âWissenschaftâ on 20th August, 2004, US biomechanics have deciphered the use of the rakish shape of the shark fin. The dorsal fin and also the tail fin with its asymmetric composition ensure the mobility of the shark. The researchers analysed the swirls of current (high-speed camera), created in an upward motion by the enlarged fin. âThe current conducts the water simultaneously backwards and downwardsâ, as explained by Cheryl Wilga and George Lauder from the Rhode Island University. âIn this way the vertical manoeuvrablility is increased.â
With fishes with symmetrical fins, swirls of current are formed around a rotational axis, however the shark allows the water to flow in a more complicated way. Two swirl centres layered above each other stabilise it with sideways (or lateral) and vertical movements (Wissenschaft 20/08/2004).
IUCN Red List of Threatened Species
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