Dorsal fin

A dorsal fin is a fin located on the backs of fish Fish

A fish is a water [i]-dwelling vertebrate [i] with gills [i], that remains so throughout its life. ...

es, whale Whale

The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of...

s, dolphin Dolphin

Dolphins are highly intelligent aquatic mammal [i]s closely related to whale [i]s and porpoise [i]s. ...

s and porpoise Porpoise

The porpoises are small cetacea [i]ns of the family Phocoenidae; they are related to whale [i]s an ...

s, as well as the ichthyosaur Ichthyosaur

Ichthyosaurs were giant marine reptiles that resembled fish and dolphins....

s. Its main purpose is to stabilise the animal against rolling and assist in sudden turns. Some animals have developed dorsal fins with protective functions, such as spines or venom. Many catfish Catfish

Catfish are a diverse group of fish [i]. ...

can lock the leading ray of the dorsal fin in an extended position to discourage predation or to wedge themselves into a crevice. Dorsal fins come in a variety of shapes and sizes.

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Encyclopedia

A dorsal fin is a fin located on the backs of fish Fish

A fish is a water [i]-dwelling vertebrate [i] with gills [i], that remains so throughout its life....

es, whale Whale

The term whale is ambiguous: it can refer to all cetaceans, to just the larger ones, or only to members of...

s, dolphin Dolphin

Dolphins are highly intelligent aquatic mammal [i]s closely related to whale [i]s and porpoise [i]s. ...

s and porpoise Porpoise

The porpoises are small cetacea [i]ns of the family Phocoenidae; they are related to whale [i]s an ...

s, as well as the ichthyosaur Ichthyosaur

Catfish are a diverse group of fish [i]. ...

can lock the leading ray of the dorsal fin in an extended position to discourage predation or to wedge themselves into a crevice.

Dorsal fins come in a variety of shapes and sizes.

Fish

Nearly all types of fish have at least one dorsal fin, although there are some exceptions, such as the knifefish. Many have two or even three fins, or the fin may be a long one that merges with the caudal fin Caudal Fin

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. A very common pattern, characteristic of the many familiar species in the order Perciformes Perciformes

The Perciformes, also called the Percomorphi or Acanthopteri, include about 40% of all fish [i] ...

, is to have a forward dorsal fin formed from sharp spines, and a rear dorsal of soft rays. See fish anatomy Fish anatomy

Fish anatomy is primarily governed by the physical characteristics of water [i], which is much denser th ...

for more details.

Whales, dolphins and porpoises

In relation to the size of the creature, the dorsal fin of the male orca Orca

The Orca or Killer Whale is not a whale, but the largest species of the oceanic dolphin [i] family [i] ...

is quite large, as much as 1.8 m high. Many captive killer whales experience collapse of the dorsal fin, possibly because lack of exercise through turning leads to diminished muscle Muscle

Muscle is contractile [i] tissue [i] of the body and is derived from the mesodermal layer [i] ...

tone. The dorsal fins of most other whales are relatively small. The bowhead whale Bowhead Whale

The Bowhead Whale, also known as Greenland Right Whale or Arctic Whale, is a marine mammal [i] ...

has no dorsal fin at all, as an evolution Evolution

In biology [i], evolution is the change in the heritable [i] traits [i] of a population [i] ...

ary adaptation to its life spent cruising under icepack.

The dorsal fins of whales develop distinctive nicks and wear patterns with time, and this fact is used by wildlife biologists to identify individuals in the field.