What is Fish?

We know you are curious about fish facts, but let us learn some basic details about fish.

Fish is an aquatic animal that doesn’t have digits or limbs, but has gills. The earliest form of fish first appeared in the Cambrian period (541 million years ago to 485.4 million years ago).

They communicate with each other underwater via acoustic signals. 


There are many species of fish. In this article on fish facts, we will not be addressing any particular fish species. This blurb will give you general facts about fish.

There are thousands of varieties of fish in this world. We can’t learn about each one of them separately in this article, but we can learn about their general characteristics, behavior, habitat, and diet. Hence, we brought fascinating fish facts list for you to read and enjoy. 

Dig in!

Scientific Classification:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Clade: Olfactores
  • Subphylum: Vertebrata

Fish Facts 1-10

1. All the fish have a backbone and they live in water. Except these two similarities, each genus and species differs from each other in multiple ways. 

2. There are over 20,000 species of fish in this world. The fish can measure from 8 millimeters or 0.3 inches to 16 meters or 52 feet. 

3. Catfish have over 27,000 taste buds. Some fish have taste buds all over their bodies. 

4. Croaker is the loudest fish. Fish don’t have vocal cords, but they use other body parts to produce sound like creak, wail, hiss, grunt, boom, and shriek. 

5. If there is not enough oxygen in water, fish can drown. 

6. It is rare, but fish can get sunburned. It happens only in water bodies which are not deep enough for the fish to swim to the deeper areas and take shelter. 

7. The spotted climbing perch can walk on land with the help of its pectoral fins and even can gulp oxygen from the air. 

8. Parrotfish produces a type of mucus. They protect themselves by covering their bodies with the mucus. 

9. A single pufferfish can kill 30 people and the toxin is 1200 times more poisonous than cyanide

10. Though jellyfish and starfish have fish in their names, they are not fish. To be a fish, the animal must have scales, gills, and backbone. Jellyfish and starfish don’t have any of these characteristics.

Fish Facts 11-20

11. Seahorse is the slowest fish. It moves so slow that if you don’t pay attention you can’t notice it moving. 

12. Sailfish swims at a speed of 110 kilometers per hour. Istiophorus platypterus or the Indo-Pacific Sailfish is the fastest fish. 

13. Did you know that fish cannot chew? If they try, they can die because chewing interferes with water that is passing through the gills. 

14. Similar to birds and mammals, they can get stressed out! Their sense of taste, sight, and touch are amazing. 

15. They also have another sense called the lateral line, which, more or less, works like a radar. It is a series of sensory cells that lie on the side of the fish. It helps them to move around in murky or dark waters. Not just that, but thanks to the lateral line, the fish catches minutest vibrations and converts them to electrical impulses. The fish are so sensitive that they can differentiate between predators, prey, and even mates. 

16. Few species like shark have to swim continuously as they don’t have an air bladder that will keep them afloat. 

17. Most of the fishes have dark dorsal side and light ventral side to escape from predation. 

18. Did you know that Antarctic icefish have antifreeze in their blood? They can live in -1 degree water permanently. 

19. Nearly 450 species of fish can change their sex as the need arises. An individual fish can change to male or female depending on the availability of another sex. If it is single, then it can even fertilize its own eggs

20. According to a research, one-third of male fish in Britain’s rivers are changing their sex. 

Fish Facts 21-30

21. Whale shark is the largest fish in the world. Whale sharks can grow over 50 feet long and can weigh over several tons. Basking shark is the second largest fish measuring around 35 to 40 feet in length.

22. A deepwater fish, often called bristle mouth, is the commonest fish. Its size is the size of a small minnow. Fishermen catch it at 500 meters or deeper. Needless to say, it is present all over the world.

23. Fish with sucking mouths like hagfish and lamprey are considered as the oldest living fish. Zoologists study them to know how life has evolved from low to advanced animals.

24. There are two ways of telling the age of a fish. Just like trees, they have growth rings on their scales or on their otoliths or the ear bones. The rings mark the changes of season in fish’s growth. 

25. The ear bones (otoliths) grow like pearls. The material added to them changes color and consistency with seasons. In summer, it is whiter and in winter, it is thinner and translucent.

26. As a fish grows, a series of rings appear on its scales. The rings are wide apart in summer and in winter the rings are close together (as they grow slowly in winters). A pair of rings mark one year.  

27. The lifespan of a fish depends on its species. There are species which live for over 40 years like Acadian redfish or over a hundred years like Orange roughy. 

28. Fish don’t have lungs. They have gills. The gills has a fine network of blood vessels that absorb oxygen from outside and diffuse it to the entire body. 

29. Fish take rest or in our words sleep. Most of the fish have a motionless life and some float at one place. Others hide in coral or mud and there are others which build nests for themselves. Though they are resting or sleeping, they remain alert. 

30. There are over 240 species of fish that are included in the no salt diets. 

Fish Facts 31-40

31. There are herbivore fish and carnivore fish. Carnivore fish like sharks use their sharp teeth to catch and hold the prey and then swallow them whole. Bottom dwellers just crush shellfish (their food) with their flat teeth. Herbivore fish don’t have teeth, but have something called pharyngeal teeth. 

32. The muscle bands of fish contract in a sequence on the alternative side of its body. This muscle contraction whips the tail rapidly side to side. Pectoral, pelvic, and vertical fins are used for stabilization. However, sometimes fish use them for fast forward movement.

33. Tunas, bill fish, some sharks can swim at a speed of 50 miles an hour for a short period of time. For continuous swimming, they maintain a speed of 5 to 10 miles an hour. 

34. Some fish can swim backwards. But they usually don’t swim backwards. The ones that can swim backwards are mostly seen in the eel family. 

35. Most fish swim horizontally. Some of the exceptions are sea horse, shrimp fish of the Indian ocean

36. There are only three types of fish mouths. They are forward facing, downward facing, and upward facing. The mouth is situated to suit their hunting. 

37. Salema Porgy is a type of bream that is native to the East Atlantic and some parts of the Mediterranean. It can invoke hallucinations similar to LSD. Romans used the fish as a recreational drug. The fish’s head is the only part that contains the drug material. 

38. In 1853, people in London, England understood the concepts of aeration and filtration of water. It was only after that humans kept fish as their pets.

39. A seahorse’s offspring is called fry.

40. We use fish and fishes both. The difference is when fish is used we are referring to just one species. For example: 10 tuna is termed as 10 fish. But when there are more species, then word fishes is used. For example: 4 tuna, 3 salmon, 8 trout are 15 fishes. 

Fish Facts 41-50

41. The ocean sunfish doesn’t have a tail. A female (sunfish) can lay around 300 million eggs each year. 

42. Seahorses can camouflage. They can move their eyes in independent directions as well. One eye looks forward and the other looks backwards.

43. Most of the seahorses mate for a lifetime. Female seahorses lay eggs inside the pouch of male seahorses bellies. When it is time for the babies to hatch, the father holds to a seaweed and rocks forward and backward till the babies pop out of the pouch.

44. The smallest fish in the world is the tiny goby of the Philippines. Its maximum length (mostly) is half-an-inch. However, it is found in such huge numbers that it supports fisheries. 

45. Hagfish is one of the slimiest animals in the world. In a minute, Atlantic hagfish can produce a bucket of slime. 

46. The first vertebrate with a skeleton of bones on Earth is fish. Earlier fish didn’t have scales, jawbone, fins, but they had a dorsal fin. 

47. Some species of desert pupfish can live in hot springs where the temperature is over 113 degrees Fahrenheit.

48. Stone fish is the most poisonous fish in the world. Its sting can cause paralysis, shock, and even death if not treated properly. 

49. An Australian lungfish lived for 65 years. It died in 2003. It is the oldest known age for a fish. 

50. Flying fish can glide 160 feet or 50 meters on an average. But they are known to glide nearly 660 feet or 200 meters. They can go as high as  19 feet or 6 meters. 


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