Dorsal fin of Shark
Depending on the species, there may be either one or two dorsal fins. The first dorsal fin is the most prominent as it is situated on the top of the animal, behind the head. This is frequently the fin that is seen sticking out of the water. The dorsal fins keep the shark upright, i.e. prevent the body from tipping or rolling over. If there is a second dorsal fin, it is much smaller and positioned further down the torso, in line with the pelvic fin. Some sharks present with spines on their dorsal fin. Usually sharks in the wild very, very rarely swim with their dorsal fins exposed above the surface. Most shark species swim fairly close to the bottom or in mid-water (the large expanse of ocean between the bottom and the surface). Left to its own devices, however, most sharks will not approach the surface at all.
About the Animal
Sharks belong to a family of fish that have skeletons made of cartilage, a tissue more flexible and lighter than bone. They breathe through a series of five to seven gill slits located on either side of their bodies. All sharks have multiple rows of teeth, and while they lose teeth on a regular basis, new teeth continue to grow in and replace those they lose. Shark ‘skin’ is made up of a series of scales that act as an outer skeleton for easy movement and for saving energy in the water. The upper side of a shark is generally dark to blend in with the water from above and their undersides are white or lighter colored to blend in with the lighter surface of the sea from below. This helps to camouflage them from predators and prey. They can detect their prey’s scent from a great distance. Sensitive eyes see clearly even in the dim light of the ocean depths.