Whenever we hear about fish, our mind thinks about the sea or water. 

Fish has a special place in all aquatic life. They are the most well-known of all aquatic animals. 

So far, at least 32,000 species of fish have been identified throughout the world. The fossil record tells us that the fish have been on Earth for over 500 million years. (Source)


Is the fish a reptile? Is fish an animal? Why don’t they live on land?

Are there any fish that are associated with mammals even when they are in the water?

Whenever we talk about fish, these questions come to our mind. 

We will answer all these questions in this post. Will you also give you information on whether the fish are mammals, reptiles, or amphibians? 

Before explaining all these questions, I would like to give you a small introduction to the fish. With this introduction, you will get a little easier to understand further information. 

So, let’s start

Short introduction about fish

If we want to define fish in simple terms, we would say that fish is an aquatic organism with gills and vertebrates and uses fins to swim. Easy right?

Fish is also very well-liked as food. Fish are aquatic organisms that breathe in gills instead of lungs.

The presence of gills is a unique feature of fish. Fishes can only live-in water, so the term aquatic vertebrates are used for them. 

Fishes move with the help of fins. Fins are small structures present on the surface of fishes.

The fish population is equal to 48 percent of the total vertebrate population. 

External fertilization occurs in fishes. In external fertilization, the ovaries and sperm meet outside the body.

Fish are cold-blooded so that they can maintain their body temperature according to the water temperature. 

You might be wondering why I am talking about all this while the topic is whether fish are mammal reptiles or amphibians? There is a logic behind this.

When you learn about fish’s introduction and life, only then will you understand why fish are different from mammalian reptiles and amphibians.

We have learned a little about the fish. Let us now answer the questions that we had discussed earlier.

Read More about Fish:

Is fish an amphibian?

Amphibia is a Latin language word that means- both. Amphibians can survive both on land and water.

Therefore, amphibians are considered to be the link between land animals and water animals.

 To know Is a fish an amphibian, we need to know about the origin of amphibians.

 So let’s know.

Origin of amphibians?

According to Wikipedia, about 370 million years ago, amphibians evolved from lobe-finned fish.

This fish was similar to modern coelacanth and lungfish. (source)

Scientists believe that lobe-finned fishes developed large fins like legs to crawl into the ocean.

In ancient times, when there was a lack of oxygen in the water, primitive types of lungs started developing in these fish.

These fish started spending most of the time in wet soil.

Thus, this process of development went on, and amphibians originated from fishes. (Source)

Now you must have known that fish is the ancestor of amphibians.

Even after learning this, we cannot call fish amphibians because the amphibians’ internal and external structures evolved very differently.

Why fish not considered amphibians?

There are different categories of fish and vertebrate amphibian animals (animals with a backbone).

As we know, the characteristics of one type are other of another kind.

Fish are very close to amphibians. But to call it amphibious will not be right, according to scientific research.

Below are some points based on which we can say that fish are not amphibians. (Except for a few exceptions, such as mudskippers fish.)

  • Fish live in water all their life, while amphibians are adapted to both water and land.
  • Fish only have gills to breathe, but amphibians have gills, lungs, and skin to breathe.
  • Amphibians can breathe from both air and water, while fish can breathe only and only underwater.

Besides, there are several other points based on which we can say that fish are quite different from amphibians.

Therefore, fishes are not amphibians. But we can say that amphibians are very much related to fishes. And amphibians must still be connected to water.

exception- (mudskippers fish)

Mudskippers fish are called amphibian fish. This fish can survive both outside and inside water. Its specialty is that its wings are like legs. Which helped to move it from one place to another. (Source)

Are fish a reptile or mammal?

Fish is the ancestor of amphibians, reptiles, and mammals. Fish cannot be included in both reptiles and mammals.

The reptile has lungs to breathe. Crawl on land with the help of four short legs. If no one has legs, they only crawl and walk.

Mammals have hair on their body.

The characteristic hair and warm blood on a mammal body make them completely different from the fish.

Mammals breed as infants while fish release eggs.

Many such characteristics distinguish a fish from a mammal and a reptile.

The classes of animals are very different from each other.

The examples of these three classes tell us that there are many differences between the primary types.

In simple words, it can be said that fish is neither amphibian nor reptile, nor mammal.

Pisces, amphibians, reptiles, and mammals are all different classes of animals.

These three classes differ from each other based on their different characteristics.


Now you must have known that why fish are not mammalian, reptiles, and amphibians.

Fish is an excellent source of protein. And it has great importance in the life of the human race.

At the same time, it is a means of economic livelihood for many nations.

Liver oil is obtained from the liver of fish in which vitamin-A and vitamin-D are abundant.

Through this article, I hope that you have got excellent information about the characteristics of fish and reptiles, mammals, and amphibians.