Dorsal Fin: Do All Fish Have It, What Purpose Does It Serve And More!

Martha Martins
Nov 02, 2023 By Martha Martins
Originally Published on Jan 19, 2022
Dorsal fin of great white shark.

The dorsal fin enhances the lateral surface of the body while swimming and helps to stabilize the fish in the water, but at the cost of increased drag.

A distinct collection of fin motor neurons that are engaged in antiphase with the motor neurons controlling the trunk muscles during movement stabilizes their position in reference to the body during movement. This is required to maintain the dorsal fin's vertical posture in relation to body movement.

A dorsal fin is a fin located on the back of most aquatic vertebrates within various animal kingdoms taxa. The dorsal fin of some teleost species extends across the majority of the body, and an undulatory wave would be delivered across the entire dorsal fin in either a backward or forward direction, propelling the fish in the desired direction.

Connective tissue makes up the dorsal fin and flukes. Another connective tissue has been lost, including external ears, and the male genitalia has relocated internally.

In dolphins, the tissue is surrounded by veins and arteries that control the blood flow to all appendages. If the animal wants to cool down, it may do so by increasing blood flow to these regions, and if it needs to warm up, it can shunt blood back to the core.

Do all fish have dorsal fins?

It is a common myth that all kinds of fishes have a dorsal fin.

Fishes with jawlines necessarily have to have the dorsal fin. Simpler fish that haven't developed the larger head adaptations of their peers frequently have suckers or no fins at all.

The bichir is an amazing example of a fish lacking a dorsal fin. Finlets are little fins found behind the dorsal and anal fins of bichirs. There are no dorsal fins and only finlets on the dorsal surface in bichirs.

Some goldfish are born with missing or deformed fins. Goldfish missing dorsal fins have been demonstrated to have slower swimming speed, slower acceleration, and more inefficient locomotion than normal goldfish. They also have to deal with a tendency to roll to the side while moving or at rest, as well as less directional stability.

There is another example of a shark surviving without a dorsal fin. It is an adult female gray reef shark.

This shark was not harmed as a result of shark finning. They're also known as the gray shark, the bronze whaler, the gray whaler shark, the longnose blacktail shark, the shortnose blacktail shark, and the Fowler's whaler shark. This type of shark is common in the Indo-Pacific, and they frequently patrol shallow-water reefs.

There are striking differences in the dorsal fin number and functionality in various fishes. The majority of fishes, including this Prussian carp, have only one dorsal fin. Sharks have two dorsal fins on average. Yellowfin tuna also have two dorsal fins. Haddocks have three dorsal fins on their backs.

The impacts of the lack of a dorsal fin on welfare are difficult to quantify. Affected fish have less control over where they are in the water and how they move.

In the wild, this would be a significant hindrance, but the impacts on quality of life in captivity are unknown. In this area, more research is required. Because the lack of a dorsal fin is a breed trait, all fishes of this breed are impacted.

What's the function of the dorsal fin?

During swimming, the dorsal fins enhance the lateral surface of the body and so provide stability.

The dorsal fin's principal function is to keep the animal from rolling and to aid in rapid maneuvers.

A dorsal fin is a single medial fin seen on the midline of the backs of many aquatic vertebrates. The dorsal fin of teleost fish develops from skin pieces that create a caudal fin fold during embryonic development.

Based on research it is seen that some aquatic species have altered the structure of dorsal fins to serve new purposes. The dorsal fin and the anal fin are used to propel the sunfish.

Anglerfish have a biological counterpart of a fishing pole and a lure called illicium or esca on the anterior of their dorsal fin. To ward off predators or wedge themselves into a fissure, many catfish may lock the front ray of their dorsal fin in an extended posture.

Dorsal fins with protective purposes, such as spines or venom, have evolved in several species. Both the spiny dogfish and the Port Jackson shark, for example, have spines in their dorsal fins that can secrete venom.

Many species of animals with dorsal fins are not particularly closely related to one another, despite having independently evolved external superficial fish-like body plans ideal for their marine environments.

It includes, most notably, fish, but in addition mammals such as large cetaceans (whales, dolphins, and porpoises), and even extinct ancient marine reptiles such as species of ichthyosaurs, through convergent evolution.

The unique nicks and wear prints that form on the dorsal fins of big cetaceans are frequently utilized by wildlife scientists to recognize individuals in the area.

Dorsal fin of a shark.

What does a dolphin's dorsal fin do?

The dorsal fin is designed to operate like a keel of a boat, allowing the dolphin to stay stable in the water.

Dolphins have a slender body that is void of many striking features. The dorsal fin's shape or curvature may also help with hydrodynamics. The obtained hydrodynamics would help these animals swim more rapidly and effectively by reducing drag.

The dorsal fin, along with the rest of the mammal's limbs, allows it to thermoregulate, or regulate its body temperature. Fins and flukes are composed of dense, fibrous connective tissue that lacks bone, cartilage, or muscle.

If the animal desires to cool down, it can increase blood flow to these regions, and if it requires to warm up, it can shunt blood back to the core.

This fin acts as an identification mark for marine animals. It helps to identify each individual dolphin because it is one of the first body components to be visible as the dolphin surfaces. This is aided by its unusual form and notch pattern on the trailing edge.

Can a whale survive without a dorsal fin?

Whales have four fins: two pectoral fins (instead of arms), a caudal fin (also known as the tail), and a dorsal fin.

The caudal fin is utilized to propel the marine animal, with powerful muscles along the peduncle that would be used to create up-and-down movements. The whales' rudders and stabilizers are the two pectoral fins.

Whales can survive well without the need for a dorsal fin. In different whale species, the dorsal fin results in serving a varied purpose.

The dorsal fin of some whales such as right whales and narwhals has completely vanished. This fin is so tiny in other species such as blue and sperm whales that it no longer serves any purpose. The dorsal fin of beluga whales has evolved into a dorsal crest, allowing the animals to breathe through thin ice.

The big dorsal fin betters the hydrodynamics of quicker species such as dolphins, killer whales, and porpoises, allowing them to glide through the water more efficiently. Dorsal, caudal, and pectoral fins, similar to elephant ears or a dog's tongue, help control excess heat during a strenuous activity like hunting.

Damage To The Dorsal Fin

The dorsal fin is composed of dense, fibrous connective tissue without bones or cartilage. The size and shape of the dorsal fin vary depending on the ecotype.

Based on current research, whales and sharks can heal from injuries at an incredible rate, even when their dorsal fins are substantially amputated.

Damage to the flanks and fins of aquarium fish can indicate failed predation attempts. 

What can we do to help fishes with hurt dorsal fins?

Damaged fins are a common aquarium injury.

Handling, fighting, fin-nipping, unsuccessful predation, and other forms of accidents and abrasions are the most prevalent causes of injury in fish.

Chasing fish around an aquarium can result in them rubbing against pebbles or colliding with the aquarium's glass walls, resulting in physical injury. Even when netted, the scales and fin membranes of aquarium fish are easily separated.

To catch aquarium fish, use the appropriate net, such as a fine net for tiny fish and a larger net for larger fish. If possible, place the fishes in a plastic container and remove them with that container rather than a net.

During the catch and shipping of wild-caught fish, they may be harmed. Broken fins and missing scales usually heal on their own without issue, and if the fish is otherwise feeding and behaving properly, it can be purchased with confidence.

The scales and fin membranes of the fish recover quickly, so no anti-fin rot or anti-fungus medicine is required unless symptoms of one of these diseases appear. If, on the other hand, the damage to the fish is significant and there are visible patches of blood or muscle, treat the fish for germs and fungus ahead of time.


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Written by Martha Martins

Bachelor of Arts specializing in Linguistics

Martha Martins picture

Martha MartinsBachelor of Arts specializing in Linguistics

Martha is a full-time creative writer, content strategist, and aspiring screenwriter who communicates complex thoughts and ideas effectively. She has completed her Bachelor's in Linguistics from Nasarawa State University. As an enthusiast of public relations and communication, Martha is well-prepared to substantially impact your organization as your next content writer and strategist. Her dedication to her craft and commitment to delivering high-quality work enables her to create compelling content that resonates with audiences.

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