All about Fish for Kids | Learn the characteristics of fish | What is a fish?

All about Fish for Kids | Learn the characteristics of fish | What is a fish?

All about FISH There are over 32,000 different species of  fish. Fish live their entire lives in water. They live in rivers, ponds, streams, and sometimes  even in a tank. Some are found in freshwater only, like a lake. While others are only found in  saltwater, like an ocean.

Fish are cold-blooded- which means their body temperature is the  same as the environment where they live. If they live in the freezing waters of the Artic,  their bodies adapt to that cold temperature. And if they live in a tropical location where  the water is much warmer, their bodies adapt to live there too. Humans are warm-blooded. This  means regardless of whether it is very cold, or very hot around you, your body temperature  always stays the same, unless you have a fever.

Fish come in a wide variety of colors, sizes, and  characteristics. But all fish have certain things in common. For one thing, they are vertebrates,  which means they have backbones, just like humans. Fish also have fins that help them move and  swim through the water. Their back fin helps push them forward, while the fins on each side  help them steer. Some fish have fins on the top and bottom of their bodies. Those fins help them  stay in place and keep them from rolling over.

Another characteristic of a fish is  gills. You use your lungs to breathe air, but fish use their gills. The gills allow fish  to breathe in water. Fish get their oxygen from the water instead of the air. When water enters  a fish’s mouth, it passes through its gills. Little fibers in the gills absorb oxygen from the  water and move it into the fish’s bloodstream. The heart then pumps the blood to move  the oxygen throughout the fish’s body.

A fish’s diet varies. Some fish, like  catfish, eat plant life in the water or algae scraped off rocks. While fish like sharks, eat  other fish as well as some mammals like seals and sea lions. The larger a fish’s mouth, the bigger  the prey a fish can eat. The lantern fish and the viper fish both eat near the bottom of a body of  water. The viper fish has fangs that are so large, they can’t even fit in its mouth. It also has a  large dorsal spine that lights up to attract fish, similar to a fishing lure. The Herring and the Mackerel both feed near the surface of the water. Their  small mouths are good for eating smaller fish.

For protection, many fish travel in  a group called a school. In a school, the fish swim close to each other. This makes them  harder to catch because a predator sees one large fish instead of many little fish. Most fish also  have scales covering the outside of their body. The scales protect the skin from attacks. They  also help the fish swim faster through the water.

Did you know that fish have ears? Both  humans and fish use their ears for balance. However, a fish’s ears are not on the outside  like yours are. Their ears are inside their bodies and are used to detect vibrations in the  water. The eyes of a fish are similar to yours. They can see color like you can. Their eyes are  also used to communicate. The male fish uses his eyes to attract female fish. Fish have a sharp  sense of smell and can detect odors in the water.

There are three different classes or types  of fish: jawless, cartilaginous, and bony. Jawless fish do not have jaws, a stomach,  or scales. Their skeletons are made up of cartilage instead of bones. Most don’t  have fins on the sides of their bodies. Instead, they have a dorsal or caudal fin.   Dorsal fins are on the middle of a fish’s back, while the caudal fin is at the back of the  fish. Jawless fish usually have long bodies. One type of jawless fish is called an eel.   There are about 800 species of eels. They are long in length from two inches to 13 feet. Most  eels live in the ocean and can swim backwards. Cartilaginous fish have jaws as well as paired  fins. They also have skeletons that are made of cartilage instead of bone, just like jawless  fish. Cartilaginous fish are covered with a tough outer skin that includes placoid scales. They  have 5 to 7 gill slits as well as two nostrils. Sharks falls into this category. Even though  the skin of a shark appears to be smooth, they are actually covered with scales  that can be seen under a microscope.

Bony fish have skeletons that are  made of bone instead of cartilage. These fish have scales as well as a single pair  of gill openings. This category is the largest class of fish with over 20,000 species. Black  Marlin and some Sturgeons belong to this group. The Ocean Sunfish is the heaviest bony fish  in the world and can weigh about 2,200 pounds.

There are some animals that many people  believe are fish because these animals spend their lives in water too, but scientifically  they are not fish. Whales, dolphins, octopus, starfish, and jellyfish do not meet all the  requirements needed to be called a fish. For example, dolphins and whales are warm-blooded.   They do not have gills either, instead they have lungs, just like you. They are part of the mammal  category. Starfish do not have fins or gills, and a jellyfish and octopus do not have backbones  or vertebrates. So, they are not fish either.

The biggest fish are sharks. Most sharks grow to  about 40 feet and weigh an average of 20 tons or 40,000 pounds. One type of shark, the whale shark,  was the largest ever measured at 60 feet long! It weighed 32 tons or 64,000 pounds!   That might seem pretty terrifying especially if you saw it  swimming near you in the water. But sharks rarely attack humans. They would  rather feed on their diet of other fish.

A small fish is called a fry. It is not  yet an adult, but it can feed itself. The smallest species of fish in the world has  a long name—Paedocypris progenetica. It is found in the waters near Indonesia and measures  only about one-third of an inch. It is a member of the carp family. It has a see-through  body and a head unprotected by a skeleton.

A common fish is a trout. A Rainbow Trout has  beautifully colored skin which gives them their name. They are able to swim very quickly upstream.   Trout are an important food source for humans, bears, and other animals. They usually  live in freshwater lakes and rivers.

Salmon might be another  fish you are familiar with. They are born in fresh water. They travel all  the way from streams and rivers to the ocean; a trip that can be hundreds of miles long. They  might then travel another 1,000 miles in the ocean to get to their feeding ground. When it  is time for them to make babies or reproduce, they then return to fresh water, and often  to the exact spot where they were born.

There are 10 different ocean species of Marlin.   These fish have long body’s and spear like snouts. Marlin can swim up to 50 mph! And some can reach  lengths up to16 feet and weigh 1,800 pounds. Glass fish are completely transparent, which  means you can see all the way through them. They are great as pets, but  they don’t like to live alone. They do best when they are  with their same species.

Many people in the world depend on fish for  food. Fish help our environment too. They are one of the biggest contributors of nutrients  to the various ecosystems near them. Fish were the first animals on Earth with backbones. And  they have existed for over 500 million years.

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