How many fins do sharks have? Sharks can have as many as eight different fins. These include two pectoral fins, a pair of pelvic fins, a first and second dorsal fin, a caudal fin or tail, and an anal fin.
Many benthic shark species lack the anal fin, and some of those belonging to the primitive Hexanchiformes order have just one dorsal fin.
What Are The 5 Main Types Of Fins That Sharks Have?
Most sharks have five different types of fins, each of which has evolved to perform specific roles or functions. These are:
The primary purpose of the fins is to provide thrust, lift, stability, steering, and propulsion. Working together, they move the shark through the water. Some sharks also use their fins to communicate and, in some cases, even walk.
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The shark’s fins have evolved over millions of years, adapting to environmental pressures to provide the most efficient and harmonious system.
Do Sharks Have Caudal Fins?
The shark’s tail is a two-lobed caudal fin that provides propulsion and thrust. The size and shape of the caudal fin are dependent on the shark’s primary habitat and hunting technique.
For instance, the two lobes of the tiger shark’s caudal fin are similar in size, creating a more symmetrical shape that researchers believe is beneficial during their lengthy migrations.
Meanwhile, the common thresher shark’s caudal fin has a vastly elongated upper lobe nearly as long as its body. It uses this weaponized fin to slap the water and stun its prey into submission.
Great white and shortfin mako sharks rely on speed to ambush their prey and so have developed lunate, or crescent-shaped caudal fins that provide maximum thrust and acceleration.
Bottom-dwelling, benthic sharks, like the nurse and zebra, have heterocercal caudal fins in which the upper and lower lobes are unequal. The smaller bottom lobe enables these species to swim unencumbered along the seabed.
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Do All Sharks Have Dorsal Fins?
All sharks have at least one dorsal fin, with most having two. The primary or first dorsal is situated roughly halfway along the shark’s back, while the second dorsal fin sits just in front of the shark’s caudal peduncle or tail stalk.
The two dorsal fins work together to stabilize the shark and stop him from tipping to one side.
The dorsal fins are so critical that some species, like the Spiny Dogfish, use poisoned spines to protect them against possible predation.
Studies also suggest that dorsal fins play a role in the reproduction process, with male sharks communicating their interest in a female by biting her dorsal fin. He’ll also bite the pectoral fin during copulation, so the whole process is quite violent.
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The dorsal fin sticks out of the water if a shark swims close to the surface, and although this is a ubiquitous image in shark movies, it rarely happens in reality.
Sharks prefer to stalk and ambush their prey, so stay hidden in the deeper water. They may occasionally “knife” the water, but they’re surprisingly sensitive to the sun, so only expose their dorsal fins for brief periods.
What Species Of Shark Have Only One Dorsal Fin?
Sharks belonging to the primitive order, Hexanchiformes, have just one dorsal fin situated close to their caudal fins. These include nurse, cow, frilled, and six-gilled sharks.
Why these sharks lack the second dorsal fin is something of a mystery, especially as it plays such a vital stabilizing role. It also improves the maneuverability of its caudal peduncle and fin.
In sharks belonging to the Lamnidae family, the small second dorsal and anal fins resemble the finlets found on high-speed scombrid fish, such as bonitos, mackerels, and tunas.
These two small fins have, therefore, have adapted to help fast-swimming sharks travel even faster. With their pivoting bases and long rear tip that floats free, these fins help the boundary layer flow over the rear end of the body, while the tips “break up fin-tip vortices by swinging back and forth.”
By doing this, these two fins reduce drag near the caudal fin and make high-speed cruising more energy efficient.
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Which Shark Species Have An Anal Fin and Why?
Not all sharks have anal fins, but those that do use them in conjunction with the dorsal fins to maintain stability. The anal fin is triangular, like the dorsal fins, and acts a little like a keel on the bottom of a boat.
Not all sharks have an anal fin, however. The 126 sharks that belong to the order, Squaliformes, all lack an anal fin, including the ancient Greenland shark and deepwater species like the Sleeper and Lantern sharks.
Precisely why these sharks have evolved without an anal fin is unknown. Many of them spend a lot more time on the bottom of the ocean than in open water.
It could be that the anal fin is too much of a hindrance or that the seafloor provides all the stability these sharks need.
What Is A Pelvic Fin On A Shark?
Sharks have a pair of pelvic fins that are the approximate equivalent of a human’s legs. This parallelism is unsurprising given that we share an ancestor in the form of a primitive fish called Acanthodes bronni.
Whereas we use our legs for propulsion, however, the shark uses its pelvic fins to control the “hydrodynamic balance at the posterior part of the body.” This stability is especially critical for large species, like Whale and Basking sharks.
Also known as ventral fins, pelvic fins provide lift and steering. They also form an emergency braking mechanism so sharks can “make quick decisive stops.”
In males, each pelvic fin has a “deeply grooved cartilaginous extension,” known as a clasper. The clasper is similar to a penis and is used to deposit sperm in the female’s body.
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The females of some shark species also use their pelvic fins before and during intercourse. Researchers have witnessed female sand tiger sharks “cupping and flaring” their pelvic fins in response to the approach of an interested male.
So-called walking sharks have developed an even more unusual use for their pelvic fins, using them to literally “walk” along the seafloor and across coral reefs.
Bamboo and epaulette sharks are amongst those that use their pectoral and pelvic fins to walk short distances. According to Dr. Christine Dudgeon, a researcher at the University of Queensland, this adaptation “gives them a remarkable edge over their prey of small crustaceans and mollusks.”
Do All Sharks Have Pectoral Fins?
While all sharks have pectoral fins, their size and shape vary considerably from species to species. The great white’s pectoral fins resemble aircraft wings, while the wobbegong’s are flat and run almost the full length of its body.
Pectoral fins provide the lift that counters the thrust produced by the caudal fin. They also help keep the shark’s body suspended in the water while controlling speed and direction.
In fast-swimming shark species, these fins have evolved to provide the most efficient way of reducing drag and generating lift.
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Although they appear relatively rigid, a shark’s pectoral fins are highly mobile. They can be curled, twisted, buckled, lifted, and lowered. Sharks can also change the angle of a pectoral fin incrementally, giving it precise control over both direction and speed.
The pectoral fins give the shark such meticulous control that it can pivot simply by combining “a slight dip of a pectoral fin” with a subtle decrease in angle of attack. Together, these movements increase water resistance on one side, enabling the shark to spin around.
The pectoral fins also generate lift at low speeds, so even large sharks, like the great white, can stalk their prey slowly and stealthily.
How Do Sharks Use Their Pectoral Fins To Communicate?
Researchers have observed some shark species using their pectoral fins to communicate. They do this by holding them in specific positions and displaying the markings on the front of their caudal and pectoral fins.
Researchers suspect that the “distinctive fin markings in whaler and hammerhead sharks… may serve as species recognition badges” or as social signals. Another study found that some shark species hold both pectoral fins “stiffly downward for prolonged periods” during an antagonistic display.
Other researchers report seeing Hammerheads using their pectoral fins in complex mating rituals, while others have observed great whites waving messages at one another.
Unfortunately, I couldn’t find any evidence to support those claims, but it is clear that the pectoral fins play an intrinsic role in mating rituals and reproduction. The male shark will often bite the female’s pectoral fin to communicate his dominance and interest and stabilize himself during copulation.
Why Does A Shark Need So Many Fins?
A shark’s fins perform many of the same functions as our arms and legs. The caudal fin provides thrust, the pelvic and pectoral fins direction, and maneuverability, while the dorsal and anal fins contribute stability.
In addition to these primary roles, a shark’s fins also perform various other functions, including communication and copulation. Some species have even developed the ability to walk using their pectoral and pelvic fins.
These fins and their functions have evolved over millions of years. In the past, primitive shark species like the Xenacanthus had a “ribbon-like dorsal fin” that ran the length of its back rather than the triangular dorsal fins we see today.
Researchers use the shape of a shark’s fin as a form of identification.
For instance, the great white’s dorsal fin is large and triangular. The straight rear edge is often torn or notched, unlike the basking shark, which has a smoother, more rounded dorsal fin that “appears to lean and flex as the shark swims.”
Meanwhile, the common thresher shark is unmistakable, thanks to the long, weaponized upper lobe of its caudal fin.
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Frequently Asked Questions About Shark Fins
How Many Fins Do Great White Sharks Have?
Great white sharks have eight fins, including an anal fin. It has no fin spines, unlike the Port Jackson shark, which has venomous spines protecting its dorsal fins.
How Many Fins Does A Dogfish Shark Have?
The dogfish shark lacks an anal fin, so has just seven fins. Like the Port Jackson shark, it has a spine in front of each dorsal fin which it uses “defensively by curling up its body and striking at an enemy.”
How Many Fins Do Whale Sharks Have?
Although the whale shark has just eight fins, it has an unusual adaptation that sets it apart from most other shark species.
A study published in Conservation Physiology discovered that the whale shark has “a high capacity to tolerate and recover from injuries resulting in extensive tissue damage.” In fact, it’s so effective that it can regrow a partially amputated dorsal fin.
Final Thoughts
Most sharks have eight different fins, each of which has a vital role to play. Caudal fins propel the shark forward while its pectoral fins maneuver it through the water, and the dorsal and anal fins provide stability.
Shark fins have evolved over millions of years, and the fins of different species have adapted to a range of different needs and environments.
The fins of the modern shark are efficient and highly specialized, with some using their caudal fins as weapons, while others use their pectoral and pelvic fins as feet.
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Nicky is a British adventurer and animal lover who spends her time exploring the natural world and writing about her experiences. Whether on horseback, underwater, running, hiking or just standing with a fishing rod in hand, she embraces everything her adopted home of South Africa has to offer.