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Sunday, November 7, 2010

Horn Sharks

As nocturnal organisms, horn sharks spend most of their day resting on a rocky bottom, in a kelp bed, or in the deep crevices of a cave or cavern. (Source) Due to their rock-like colors, the horn shark can remain in the same spot all day, blended in with its surroundings and safe from predators. (Source)  Scientists believe that each matured horn shark returns to the same resting spot day after day.
         While a horn shark may only be 15-17 cm when born, it can grow up to 3 meters by the time it has fully matured. (Source)  This is still comparatively smaller than other sharks in the ocean and, because of that, many organisms—such as large fish or sharks—can be a threat to the horn shark. Horn sharks are known for their square box-like heads, two dorsal fins, a pectoral fin, and an anal fin. (Source)  Of these distinguishing factors, the most well known features are the dorsal fins.
         Each dorsal fin contains a large spine that is extends several centimeters above the shark’s body. Because the teeth of the horn shark are not sharp enough to penetrate and seriously hurt a predator, the spines located on the dorsal fins become the most important defensive mechanism of the horn shark. When a predator attempts to eat a horn shark, the shark stabs the inside of the predator’s mouth with its spines, causing intense pain to the predator. The predator then releases the unharmed horn shark—resulting in an injured predator, but a safe horn shark. (Source)
         Horn sharks pose little threat to humans. It is rare that a human would ever come in unintentional contact with a horn shark because of their location in the deepest region of the ocean. Divers have gotten very close and have even hand fed the horn sharks safely. However, on occasion, a horn shark has been taunted and harassed resulting in an attack. To date, a horn shark has reportedly bitten only one human. (According to the International Shark Attack File) (Source)

         Besides being of little danger to humans, they are also of little importance to humans. Fishermen only occasionally catch horn sharks when trawling on the bottom of the ocean. When this does occur, they either throw them back into the water or keep them as fish bait. (Source) The only other use of horn sharks by humans is for scientific study—due to their lifespan of up to 12 years—or in exhibit tanks at aquariums.  (Source

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