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Tuesday, January 19, 2010

Flying fish


Exocoetidae, aptly known as flying fish, are a marine fish family comprising about 64 species grouped in seven to nine genera. Flying fish are found in all of the major oceans, particularly in the warm tropical and subtropical waters of the Atlantic, Pacific, and Indian oceans. Their most striking feature is their pectoral fins, which are unusually large, and enable the fish to hide and escape from predators by leaping out of the water, taking short glided flights through air just above the water's surface. Their glides are typically around 50 m (160 ft), but they can use updrafts at the leading edge of waves to cover distances of at least 400 m (1,300 ft).



Gliding Mechanism

In order to glide upward out of the water, a flying fish moves its tail to up to 70 times per second, which "vibrates" to produce enough speed to burst through the surface. It then spreads its pectoral fins and tilts them slightly upwards to lift itself to glide through the air. This permits it to sail above the ocean's surface where it can travel at speeds of more than 70 km/h. The fish is able to increase its time in the air by travelling against or at an angle to the direction of updrafts created by a combination of air currents and ocean currents in which the "wings" flutter due to the wind with a maximum glide time recorded to be 30 s.At the end of a glide, a flying fish folds up its pectoral fins which have been acting like "wings" to reenter the sea or drops the lower end its tail into the water where it "vibrates" the lower part of its tail to allow its body to reaccelerate and change direction, providing the thrust to lift itself for another glide.The aerodynamic shape of a flying fish "wing" is comparable to that of a bird's wing as bones of the fish produce a curved profile that helps generate lift during flight.Flying fish also have been recorded to glide 6 metres above the sea where some accounts have them land on ships' decks. A number of differences exist for the flying fish to glide. This depends on the number of fins it has which act as "wings" when out of the water. Genus Exocoetus has a pair of fins and a streamlined the body to optimise for speed while Cypselurus has a flattened body and two pairs of fins which maximises its ability to lift itself out of the water. At best, the longest known glide made by a flying fish genus Cypselurus is reported sailing 200 m or more.

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