Difference between Fishes and Sharks

Key difference: Sharks are a type of fish. The difference between sharks and fishes is based on their bones, skeletons, and skin texture and body shape.

Sharks are an exclusive breed of saltwater fishes; they belong to the class ‘Chodreichthyes’. Sharks are considered as living fossils, because of their evolution on Earth was 420 million years ago. There are more than 440 species of sharks distributed through all the waters of the sea.

Sharks, generally, prefer salty waters, with an exceptions of bull shark and river shark, who can survive in both seawater and freshwater. They are usually found in the deep ends of the sea. They range from small size to 17cm in length; the whale shark is one of the largest fish in the world, which is 12m in length. Their powered and shaped streamlined body makes them fast swimmers. They have massive bodies, with strong muscles and fins. They breathe through five to seven gill slits.

Sharks have lightweight cartilaginous skeleton, and the oil-filled liver which provides buoyancy to improve their fluid dynamics. Unlike other fishes, they have replaceable sets of teeth. Because of their extreme abilities to swim and prey upon other fishes, sharks are said notorious in nature and killing. Some popular species of sharks are the great white shark, tiger shark, blue shark, mako shark, and the hammerhead sharks.  

Fishes are the members of a paraphyletic group, which is composed of all gill-bearing aquatic animals. They can be further classified as lampreys, cartilaginous and bony groups.

Fish are abundantly found in all water bodies or aquatic environments such as high mountain streams, abyssal and the deepest oceans. They are ‘ectothermic’ in nature and exhibits huge diversity among its species. They are soft bodied and posses notochords which makes them more agile. They are classified under the paraphyletic category. As the term ‘fish’ is not defined under a proper grouping, it excludes the tetrapods i.e., the amphibians, reptiles, birds and mammals, from its category.

Fishes are an important food source for humans worldwide. They are commercially and substantially used through wild fisheries, or farming in ponds, or in cages in the ocean. They are also caught by recreational fishers to be kept as pets, or be raised by fish keepers and be exhibited in public aquaria. Fish also have an important role in our culture through the religious symbols, and as the subjects of art, books and movies.

Comparison between Fishes and Sharks:

 

Sharks

Fishes

Scientific name

Selachimorpha

Oreochromis aureus

Evolution

They evolved 450 millions years before.

They evolved 40-6 millions before.

Mouth

Sub-terminal mouth with rows of sharp teeth embedded in the gum.

Terminal mouth and tiny teeth on the jaw.

Skeleton

Cartilage only

Bones and cartilage

Fin and denticles

Asymmetric caudal fin and dermal denticles to cover the skin.

Symmetric caudal fin and no dermal denticles.

Body

Massive bodies

Small bodies

Swimming

Can only swim forward.

Can swim forwards and backwards

Buoyancy (floating)

Large oily liver

Gas-filled swim bladder

Gills

Gill slits but no gill cover

Covered gill slits

Reproduction

Eggs fertilized in female's body.

Eggs usually fertilized in the water.

Skin

Rough, sandpaper-like placoid scales

Slippery, overlapping scales

Muscles

Muscles are white in color.

Muscles are pink to red in color.

Waste

Nitrogenous waste is urea.

Nitrogenous waste is ammonia.

Image Courtesy: petkaria.com, the-science-llama.tumblr.com

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