Different Type Of Fish: A 400 Million Years History

Different Type Of Fish

Welcome to my website. Today’s topic is – DIFFERENT TYPE OF FISH: Fish is one of the oldest creatures on earth. They are on earth for a very long time, scientists even say, more than 400 million years.

With the changing times, they changed and evaluated and in present times there are almost 33,600 species or more are present on earth.

In different places with different environment and atmospheres, fish adopted themselves and exhibits a wide range of diversity. The most interesting fact about fish is that they are available in every corner of the world, with different shape, size, characters, and habits. But, they are everywhere.

In this article, we are going to learn about the different type of fish in details.

So, let’s get STARTED!

What Is Fish And How Did They Come?

The first species were found a long time ago in the Cambrian era. That time they were chordates, not fully developed vertebrates.

They had notochords instead of the real spine. By the time of Paleozoic Era, these beings started to become more fish like or more likely to say, like today’s fish.

During this era, fish started forming different size and shapes and by the end of this era, they had developed an external layer working as armor, which we know as scales.

So, in these contexts, we can say, any cold-blooded, limbless vertebrae with our without gills, who live fully or partially in the water can be called fish.

Different Type Of Fish

Different Type Of Fish: A 400 Million Years History

Fish can be classified depending on many factors. Habitat, edibility, poisons, size or shapes and many more.

But in a general sense, the main classification is based on the habitat.

01. Depending on habitat (Different Type of Fish):

Depending on the habitat, fish can be divided into two categories, such as-

Freshwater fish:

Fish that mainly inhibit mostly in freshwater are called freshwater fish. These fishes are mainly lean due to their movement. Some of the freshwater fish are-

  • Bass
  • Perch
  • Pike
  • Smelt
  • Sturgeon
  • Trout, etc.

Saltwater fish:

The fish that lives in the seas and oceans are called saltwater fish. They are mainly oily in nature as the high salt concentration in water helps them float.

These fish varies in sizes, from small anchovies to larger whales.

02. Depending On Shape (Different Type of Fish):

Depending on shape fish can be divided into two categories-

Round fish:

Round fish are those which are cylindrical in shape and round in cross-section. Most of the fish we eat or see are round fish. Example- Bass, Catfish, Arctic char, Cod, Haddock, Herring, Sardines, Tilapia, Trout, Red Snapper, Salmon, Swordfish, etc.


Flatfish are mainly marine species which are flattened in shape and has both eyes on the upper side. They usually reside on the seabed. Flounder, Sole, Halibut, and Turbot are some of the most renowned flatfish species.

03. Depending On The Flesh Type:

Fish can be categorized into two types depending on flesh type, such as:

Different Type Of Fish: Whitefish


Generally demersal fish or those species which live on the bottom or near the bottom of waterbody are called whitefish.

These fish have white lean meat and lesser to zero oil content.

Whitefish include Bream, Cod, Flounder, Haddock, Hake, Halibut, Monkfish, Pollack, Sea bass, Sole, Striped Bass and many more.


Bluefish indicate the general group of fish having more percentage of oil in the body.

They usually have a bluish color on the skin. Bluefish tend to have omega 3 fatty acid which is amazing for brain development. Notable bluefish are trout, salmon, sardines, eel, mackerel, herring, tuna, etc.

04. Depending On Migration:

Depending on migration fish can be classified in following categories-


The spend their entire lives in the marine water but migrate to fresh water during spawning season to lay eggs. For example, the sockeye salmon migrates 3600 km to spawn.


These species live in freshwater but travel to the marine water to spawn. Freshwater eels are such species.

05. Shellfish:

Shellfish are those which have an outer shell or exoskeleton.

They are a mainly marine animal but some species are also found in freshwater. Although technically these are not fish as they do not exhibit the general characters of fish.

There is a wide range of shellfishes available in the world but some most notable species are Clams, Mussels, Oysters, Scallops.

06. Depending On Food Habit

Fish eat a wide range of food and depending on food habit they can be divided into-

Carnivorous fish:

In a general sense, they eat meat. These fish can not absorb nutrition form plants. They need to live food. Usually, they have a big jaw with sharp teeth. Pike, gars, sharks, dolphin, etc. are some examples of carnivorous fish.

Herbivorous fish:

The fish living on plants are herbivorous fish. They are totally dependent on plants, algae or phytoplankton. They have flat teeth to grind the food before swallowing. Some of the herbivores are clownfish, parrotfish, surgeonfish, gill, etc.

Omnivorous fish:

Omnivorous fish are those which eat both plant and animal kind of food. Catfish and piranhas are notable omnivorous fish.

07. Poisonous Fish (Different Type of Fish):

These are the fish having poisonous substance in their body which can harm or even kill other living beings by being eaten or even touched.

Pufferfish, stonefish, lionfish, stingrays, boxfish, trunkfish, etc. are some very poisonous fish species.

Frequently Asked Questions

01. What is the largest and the smallest fish in the world?

Answer: The largest fish in the world is the whale shark. They can grow up to 50 feet long or more weighing tons.

The smallest fish is goby. They are merely half an inch when fully adult. They live in fresh and brackish water.

02. Are whales fish?

Answer: Most of the people mistake whale as fish because they live in water and looks like fish when in fact they are not. Whales are marine mammal animal.

Like other mammals, whales have warm blood, need air to breathe, give birth and produce milk to feed the child.

03. What does exotic fish mean?

Answer: Exotic fish are those which are not native of an area but were introduced by accident or careful planning. For example, tilapia is originally a native species of Africa but was later introduced in the USA.

Final Words

Although these are the known different type of fish, there might be many more little known or undiscovered species in the world. Every day scientists are finding new species in the wide oceans.

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