SHARK FINS
The most recognized part of a shark is the dorsal fin, often seen neatly slicing the surface of the water. Sharks also have a caudal fin (tail fin), an anal fin (not all species), a second dorsal fin (in some species), a pair of pectoral fins, and a pair of pelvic fins. The pectoral, pelvic, dorsal, and anal fins help the shark to maneuver, turn, swim straight, and move up and down in the water column. The fins are fixed and remain hard at all times, but there are some muscles that allow for subtle movements. The caudal fin provides the thrust needed to propel the shark through the water.
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Caribbean reef shark photo by Jillian Morris
Keratin based elements (ceratotrichia) support a shark's fins. It looks like dry spaghetti running through the fin. This is what shark fin soup is made from.
What is a heterocercal tail?
When a shark's vertebral column (essentially their backbone - which is made of cartilage) passes into the upper lobe of the caudal fin (tail) - this is referred to as a heterocercal tail. For most sharks, the upper lobe of the caudal fin (tail) is longer than the lower lobe. However, some faster swimming species of sharks, like the shortfin mako and great white, have a larger lower lobe on their caudal fin. Although the lobes may differ in size between species, they still have a heterocercal tail.
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What is the caudal peduncal?
The caudal peduncal is where the narrowing of a shark's body meets the tail. All the force generated by the sharks muscles is translated to the tail via the caudal peduncal.
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In general, the body shape of a shark will determine their lifestyle.
Fast swimming, open ocean species, like the shortfin mako and great white, have a conical head, large thick body, large pectoral fins, a narrow caudal peduncal with keels and symmetrical caudal fin. This is the most efficient body shape for moving quickly though the water. Moderate swimmers like blue sharks and tiger sharks have a more flattened head, thinner body, thicker caudal peduncal with little or no keels, large pectoral fins, and an upper lobe which is larger than the lower lobe. These sharks have the broadest range of swimming speeds. Slow swimming sharks like the nurse and leopard sharks have large heads with blunt snouts, pelvic fins positioned more forward, dorsal fins set farther back, and a highly asymmetrical caudal fin with no lower lobe. Sharks that live on the bottom such as angel sharks, have a flattened body, large pectoral and pelvic fins, no anal fin, and a reduced tail section.
DORSAL FIN
The fin on the back (top-dorsal side) of the shark is used for stability, balance and to assist in making sudden turns. Sharks can have 1 or 2 dorsal fins depending on the species.
PECTORAL FINS
These paired fins are located just behind the gill slits and act as the steering wheel. They allow the shark to move up and down in the water column and can also help maintain stability at higher swimming speeds. Some sharks have fairly flexible pectoral fins (epaulette and nurse - bottom left and right) and can even use them to walk!
PELVIC FINS
These paired fins help with stability and lift and are located on the underside (ventral) side of the shark.
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ANAL FIN
​This fin is located between the pelvic fins and the caudal fin and provides stability. Not all sharks have an anal fin.
CAUDAL FIN
This is the shark's tail fin which is used to move the shark forward. Some sharks (nurse sharks) do not have the lower lobe of the caudal fin.
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