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Amazing World of Fish

Fish rule the world. That is, they’re one of the oldest animal families to live on Earth. They were here long before the dinosaurs – about 500 million years ago — and they still thrive. There are over 25,000 known species of fish. There are probably many more that we haven’t discovered yet.

Freshwater Trout Fish Image - Science for Kids All About Fish
Trouts are freshwater fishes. They live in lakes and rivers.

Fish are vertebrates. That means they have a backbone. But unlike mammals, fish don’t have lungs. They breathe by taking oxygen from the water in through their mouths, where it passes over the gills. The gills then absorb oxygen from the water and send the oxygen throughout the body. Some fish are carnivores. They eat other fish and small animals and insects. Other fish are omnivores, eating both plants and animals.

A School of Salmons Migrating Image
Salmon fish migrate every year to breed and lay eggs.

Fun Facts About Fish for Kids

  • Fish are cold-blooded like reptiles and amphibians. They can’t control their body temperature.
  • Some fish live in salt water, such as halibut and cod. They live in oceans and seas. Freshwater fish, such as trout and catfish, live in lakes and rivers.
  • Salmon migrate every year to breed and lay eggs.
  • Fish have a good sense of taste, sight and touch. They can feel pain.
  • The largest fish is the great whale shark. It can grow to 50 feet long. The tiny Philippine goby is about the size of your pinky fingernail.
  • Fish are abundant in most water bodies. There are over 33,600 described species of fish. It is the greatest species diversity than any other vertebrates group.
  • Some flatfish can easily hide on the ocean floor by using camouflage.
  • Fish can communicate with each other through the use of acoustic communication. Acoustic communication includes the transmission of acoustic signals in fish from one individual of a species to another.
  • The sounds emitted by fish are a means of communication most often used in the context of feeding, aggression or courtship behavior.
  • Fishes have smaller brains, relative to their body size, in comparison to most other animals.
  • Clean fishes help other fish in removing parasites and dead skin from their scales.
  • More than 1000 species of fishes are threatened of extinction.
  • Jellyfish and Crayfish have the word ‘fish’ in their name but they aren’t fish actually.
  • Mermaids are a mythological creature with the upper half of a woman and the tail of a fish.
  • Tuna, a species of fish can swim at the speed of up to 70 kph (43 mph).
  • Fish can be found in nearly all aquatic environments from high mountain streams to the deepest oceans, however vast parts of our oceans have yet to be discovered. As deep sea engineering improves we can continue to expect more species to be discovered.
A Couple of Small Philippine Goby Fishes Image
The tiny Philippine Goby is about the size of your pinky fingernail.

Fish Vocabulary

  1. Thrive: grow and live well
  2. Vertebrate: an animal with a backbone
  3. Cold-blooded: unable to regulate body temperature
  4. Migrate: temporarily move
A Sea Horse Underwater Image
Despite their horsey shape, sea horses are fish. They have very small fins and can’t swim fast.

Learn More All About Fish And Their Major Types

Watch an intriguing video about how the seahorses got their body shape:

A video documentary about the anatomy of a seahorse.

Fish Q&A

Question: Are seahorses fish?

Answer: Despite their horsey shape, sea horses are fish. They have very small fins and can’t swim fast.


Question: Do people ever farm fish?

Answer: People farm, or raise, fish in the ocean, as well as on land. Large man-made pools or tanks are called hatcheries. Fish are born and raised here to sell as food.


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