How Are Fish Adapted To Their Environment?

Fish are classified as aquatic vertebrates that have existed for long years. The mixture of their gills, scales, and the fact that they live only in water makes it their trait that is different from all other animals. They are adapted to travel effectively under the water and to have a good sense of their surroundings.

Different characteristics and features of fish also evolved from time to time to help them avoid predators. They can also be able to live suitably in the water environment and acquire all their needs to survive.

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Fish anatomy adapts to allow other species in marine life to thrive in their own habitats. Like many animals, they have adapted to live depending on their types of chosen habitats.

For example, in certain areas of lakes and rivers, or big bodies of water like the saltwater. According to studies, there are over 160 species of fish, each with their own unique and distinct characteristics and capabilities.

What Is Adaptation?

Adaptation is a process of change. It takes place over a very long period of time and may even occur for millions of years through a process called natural selection.

These changes will affect all organisms and life forms and it can change not just the physical attribute but also its mental behavior. It’s when some life form undergoes a certain change to fit in their environment.

This is a very important process in the upbringing of an organism, if they failed to evolve over a long period of time and still didn’t get fit in a chosen environment, they will eventually become extinct.

Habitat is the surrounding or environment an animal or plant decided to live in. When it changes, any organism that is able to adapt will most likely survive.

In the natural selection process, the changes in their physical attribute and mental behavior that adapted well in a particular habitat will be kept or passed on to the next generation of an organism. Sometimes it evolves and changes over time depending on their needs.

Adaptive Features Of A Fish

Fishes are prime examples of these adaptations because they show a lot of changes over a long period of time to help them survive and avoid predators in the water environment.

Most physical changes appeared in their mouths, gills, body shape, color, senses, and locomotion. These key changes are vital in their habitats for them to survive.


Fish have gills. Like any living life form in this world, fish need a supply of oxygen in order to breathe and survive. A gill is part of aquatic organisms’ anatomy that takes oxygen from the water and excretes carbon dioxide.

The gills of a fish consists of a number of slits not more than eight to help them breathe underwater. These slits are connecting the pharynx to the outside on the other sides of the fish head.

As fish swims in the water, they open their mouth and water passes from it directly into the gills. As we know, water consists of oxygen. The oxygen that’s in the water, passes through the thin layers of gills and goes straight into the blood supply giving them enough oxygen flowing through their body.

Oxygen in water only consists of 4 to 8 parts per million, this is way off compared to the ones present in the atmosphere which is about 20% capacity.


Fish go on the daily process of changing their color for a long period of time. It’s one of the proofs that natural selection really does happen. It’s one of their skills and tactics to help them avoid such predators.

One good example of this is fish do have multiple colors depending on where you’re looking at them. They are normally dark at the top of the water and light at the bottom. It is called countershading.

One unique skill they possessed is called camouflage. This is a process where they adapt their whole body to blend in and hide for their predators. For example, pickerels and bluegills have some vertical stripes in their body to help them hide in vegetation and corals.

They also used this skill not just to avoid predators but also to hide from their prey. Fish can be both prey and predators at the same time.

Another skill that they adapted over the period of time is by changing their color patterns and texture in their body. This helps them to attract a mate and give them a better chance of reproduction. Variation of patterns also can be used to identify if the marine species is a male or a female.


Fish has changed and adapted its mouth over millions of years. This developed from time to time as they changed their needs depending on their habitat. Freshwater fish that particularly eat insects or larvae have different mouth anatomy than fish that are from the saltwater habitat.

One good example of it is the walleye, they have a huge jaw with a strong elaborate set of teeth to help them catch its prey. Some fish don’t have teeth at all, just a round vacuum-like structure of their mouth.

These fish actually suck up all organic and algae materials from the bottom or up the surface of a swamp or stream.

Body Structure

The shape of the body can also be considered an adaptation and evolution for fish species as it is one of the most important adaptations a fish may go through.

This is helpful for a lot of marine species especially the ones that have an elongated body, this helps them to swim and move through the water efficiently.

Many fish that have issues with their agility developed a spine that predators may have issues when they tried to attack. Others have a thin body where they can be able to hide in narrow and tight spaces to avoid getting eaten by predators and can also be the predator to prey upon others.

One thing also they adapt are their fins, their location and shape vary from one another. The general anatomy of fish consists of a dorsal fin that is located on their back and pelvis and anal fins on their undersides.

They also developed pectoral fins near their gills and a caudal fin located in their tail. These fins can be eminent parts of the body structure. They developed depending on their needs. The texture and size of their scales rely on how they adapt to their environment.

Sense Organs

Humans rely on their sense of sight, it is one of the most important parts of everyone’s senses. This is also very important to marine life forms as light does not penetrate or reach even the bottom and depths of the ocean.

This is why they developed a rare and very distinct sense of smell. They have more sensitive noses than humans.

For example, you’ve seen some movies about sharks, that they were able to detect even a slight amount of blood in the water. This is because they developed over the period of time such a distinct array of sense of smell using these sensory pads to know danger.

Some of the species developed a sense of vibrations into the water.


The ideal structure of a marine fish is somehow streamlined to how it moves. Most fishes, for example, a Trout or a Minnow, can swim in water for approximately 10 body lengths per second, this is an evidently impressive quality and performance any fish can do to human standards.

But if you think about it, these speeds can be roughly translated into kilometers per hour. It means that 30cm is equal to 1 foot. Trout can swim only about 10.4 kilometers per hour. Again, as a general rule, the bigger the fish, the faster it can swim.

Depending on their bodies, their agility relies on their ability to move in the water. Animals like whales and dolphins share a similar structure of a fish but evolved more from the non-aquatic animals, they do have some resemblance to fishes. It is called convergent evolution.

It is basically an evolution of similar structures organism but unrelated species in the totally same environment. Evolutions of fish rely more on how they can swim rapidly in water. Some fish that don’t tend to travel or migrate tend to have a rounded tail for quick acceleration and stopping.


Fishes are adapted to move precisely and sense their habitat under bodies of water. They evolved to be able to meet their needs and be able to help them survive for another day.

Overall, life finds its way either you’re a marine life form or just a human being. It’s natural selection, a natural process that will keep on going and evolving. A lot of fishes and all marine species do evolve for the same reason, survival. You might either be left out and become extinct or move on and go with the process of the life cycle.