67 Interesting Facts About Fishes That Most People Don’t Know

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The ocean is a vast and mysterious place– but did you know that we’ve only explored less than 5% of it? From the information we have gathered about fish, it’s safe to say that there’s much left to discover. However, here are 67 interesting facts about fishes that we do know. 

Quick Fact: You can use the word fishes when referring to several fish species.  

Interesting Facts About Fishes

After reading through this post, you’ll become somewhat of a fish expert. Ok. Hold your seahorses, perhaps not on a marine biologist expert level, but a decent amount of info to impress your fishing buddies or classmates.  

1. Fish Have Insane Sensory Capabilities

Fish have an acute sense of smell, far superior to humans. They can also see quite well, and in color, some species can even see ultraviolet light. Most fishes use a lateral line system to sense gentle currents, vibrations, and motions. 

Sharks can detect frequencies between 25 to 50 Hz through their lateral line system. 

2. Some Fish Can Live in Both Salt and Freshwater

The type of fish that can adapt to various salinity is called euryhaline species. Examples of these fish are salmon, flounder, striped bass, and eels, which can survive in environments ranging from lakes to rivers and oceans.

3. Fish Have Fantastic Communication Skills 

The most common way fish communicate with each other is through gestures and motions. However, some fish can communicate through synchronized swimming, electric pulse signals, and by releasing certain chemicals. How’s that for a chattering fish fact?

4. Fish Are Smarter Than You Think

How bright are fish really? Well, probably a lot smarter than you think. Fish have cognitive abilities, such as memories, that are more advanced than many terrestrial vertebrates. They can have long-term complex social relationships, and for example, some seahorses will partner up for life. 

5. Fish Have Longer Memory Spans Than You Think

It is widely believed that fish have a memory span of 30 seconds. Recent studies suggest that fish can actually remember certain things for up to 12 days. 

6. How Social Are Fish?

Fish form social aggregations known as shoals, consisting of fish with similar morphologies. So if you want to be part of the club, you better look and act the same. 

7. Fish and Farming

Did you know that fish farming is the fastest growing area in animal food production? Fish farming falls under aquaculture, which entails that you raise fish commercially in an enclosure that will eventually sell as produce.  

8. Good for Our Ecosystems

Fish are essential for our ecosystem as they play a vital role in nutrient cycles. A nutrient cycle describes how nutrients are continuously exchanged and moved from the environment to an organism and then back into another environment. 

9. There Are Lots of Fish in the Sea 

There are currently over 33,000 species of fish, and scientists have estimated that there are about 3.5 trillion fish in the ocean.

10. Fish Are Cold-Blooded

Most fish are cold-blooded; this is what we were taught in school. However, 35 species are warm-blooded, including the moonfish. 

11. Why Fish Have Scales

The scales on a fish help protect it from environmental factors and predators. The scales are like a “suit of armor” and act as camouflage in many environments. 

12. The Biggest Fish in the Ocean 

The biggest known fish is the whale shark which can grow up to 33 ft in length, and adults can weigh up to 41,887 lb. 

13. The Tiniest Fish in the Ocean

Known as the world’s smallest vertebrate is the stout infant fish. This tiny fish can only grow up to 7mm long. 

14. Majority of Fish Do Not Have Eyelids

Most fish don’t have eyelids as they do not have any use for them since their eyes are constantly moist underwater. 

15. Fish Are Vertebrates

Neotropical fish (freshwater fish from tropical regions) make up 10% of all vertebrates on earth.

16. Fish Can Actually Drown

This fact might be hard to believe, but it’s true. Technically it’s not drowning, but rather a lack of oxygen. 

Let me explain more. It can happen when water passes through the gills of a fish, and it absorbs the oxygen from the water. It can also happen when its gills are damaged, or water cannot move across. In either of these cases, the fish will die from not getting enough oxygen. 

17. Jellyfish, Starfish, and Cuttlefish Are Not Actual Fishes

These sea creatures may have “fish” in their name, but they are far from it. For example, fish are vertebrates, while jellyfish are dome-shaped invertebrates. 

18. Some Species of Fish Lay Their Eggs on Land 

Some freshwater and shore fishes lay their eggs among plants. The eggs are semi/adhesive, so they stick to plant leaves. This is a great way to keep the eggs from being eaten by bottom feeders.  

19. Early Fishes Did Not Have Jaws

About 440 million years ago, fish started developing jaws. Early fish relied on filter-feeding from the seabed rather than biting down on their prey. Today there are still some species that haven’t evolved yet, such as the hagfish and lampreys. 

20. Fish May Have Evolved from Sea Squirts

Scientists have speculated that fish may have evolved from a coral-like sea squirt. This is due to the sea squirt’s larvae resembling that of early fish. 

21. Weird Fish That Some People Enjoy Eating

Many people enjoy eating lamprey and hagfish In some European and Asian countries. Lamprey pies, made from sea or river lampreys, were a delicacy for the wealthy in medieval England. 

22. Some People Eat Toxic Fish That Can End Their Lives

Yes, this one’s bizarre but true. Many people consume dangerously toxic puffer fish intentionally at the risk of losing their lives. In fact, it is a delicacy in Japan, where trained chefs prepare it and serve it raw or cooked in a soup. 

23. Symbol of Pisces is a Water Sign For Fish

The origin of the Pisces fish originates from Greek mythology. The two fish represent Eros and Aphrodite, who were transformed into fish by Zeus. Its symbolism draws from two fish swimming away from each other, which is said to symbolize the division between fantasy and reality. 

Check out these Ancient Greece facts if you find this fact intriguing. 

24. Fish and Mesopotamian Mythology

Fish are an occurring theme throughout Mesopotamian mythology. This is due to the Euphrates and Tigris rivers, which the Mesopotamia civilization relied on for water, food, and agriculture. Fish was their primary food source during these times, so it makes sense why it features so heavily in their stories. 

25. Some Species of Fish Can Live Out of Water

Quite a few species can manage swimmingly out of water for short periods. Some fish with this unique ability include the walking catfish that can walk around dry land for hours and the lungfish that can survive out of water in a dormant state. 

26. Fish Can Feel Pain Too

Just like humans, fish appear to feel pain too. Although it’s not the same type of pain, fish have neurons that can sense intense pressure, high temperatures and other potential harms. 

27. Fish Have Tiny Sized Brains

Fish have tiny brains in comparison with their body size and other vertebrates. The size of a fish’s brain is about one-fifteenth of other birds and animals of the same size. 

28. How Do Fish See?

Fish see the same way that we do. They also have an iris, cornea and pupil that absorb light and signal the information to the brain. Fish have excellent daytime vision, and some tropical species can distinguish between human faces. 

29. Why Are Fish So Slimy?

The slimy mucus covering a fish allows them to swim smoothly without dragging or other organisms attaching to them. 

30. Fish Use Countershading

Fish use countershading as a form of camouflage. Countershading, a term coined in the 1800s, described an animal with both dark and lighter shades on its body.

31. Fish Can Get a Sunburn

Fish can get sunburnt, especially if swimming in ultra-clear waters. Or if they’re swimming near the surface, such as the Arctic Charr. Like humans, fish also have melanin that protects their skin from UV rays; the only difference is that we get a tan, but fish get dark spots. 

32. Fish Like To Keep Clean

Fish like to keep each other clean. The cleaner fishes would often remove parasites from other larger fish. These larger predatory fish are aware of the cleaner ones and won’t eat them as they benefit from being cleaned up. 

33. Some Sharks and Rays Can’t Stop Swimming

Literally- their lives depend on it. Some sharks and rays must keep moving to allow oxygen-rich water to continue flowing through their gills.

34. Sharks Have Eyelids 

Sharks are the only fish to have eyelids. Even though they never blink, the eyelids protect their eyes from damage. Some species of fish have unique thick, transparent eyelids that act like glasses to help them focus on objects. 

35. One Fish Can Kill You With a Single Sting

We introduce you to the stonefish, one of the most venomous creatures to exist and fatal to humans. If you are stung by this deadly fish, you’ll immediately experience excruciating pain and swelling, with your only chance of survival a large amount of anti-venom. 

36. There Are Many Pretty Fish in the Sea

There are so many beautiful and colorful fish in the ocean. And some of the most gorgeous fish to draw anyone’s attention are the mandarin fish, clown triggerfish, fantail guppy, betta fish, and cherry barb. Which fish do you think is the prettiest? 

37. Most Dangerous Fish Species

Apart from the stonefish, there are many other ocean predators and critters you’d want to steer clear from. Some of the most dangerous fish are the puffer, red lionfish, great white shark, piranha, tigerfish, candiru, and the moray eel.  

38. The Electric Eel Current 

Electric rays from an eel are so powerful that it has enough electricity to kill a horse. An electric eel can generate hundreds of volts, up to 500 V. A few jabs of these electric currents can cause respiratory or heart failure, which is fatal to some humans; however, death by eel is infrequent.  

39. A Shoal of Fish Or a School of Fish?

You’re probably more familiar with a school of fish. But when aquatic creatures such as shrimp and fish swim in larger groups, this is known as a shoal. The largest school ever formed was by the Atlantic herring species, which grouped in hundreds of millions of fish– which scientists classify as a mega-shoal.  

40. Do Flying Fish Actually Fly?

Short answer- no. But you’re probably wondering why these fish were named “flying fish” if they do not fly. Instead, they propel themselves out of the water at high speeds, reaching more than 35 miles an hour. Then they use their “wings” to glide for about 650 feet through the air. 

41. Antarctic Icefish Are Pretty Interesting

According to research, Antarctic Icefish are the only known vertebrates lacking haemoglobin and red blood cells. 

42. Clownfish Live Dangerously

Clownfish survive by living in a symbiotic relationship with the highly toxic sea anemones. The anemone protects the clownfish from predators. And the clownfish attract these predators with their bright colors, leading them straight to the anemone’s poisonous clutches, where they are killed and eaten. 

43. How To Tell If A Fish Is Happy?

There are sure tell-tale signs that can show you if a fish in a tank is happy:

• Fish breathe regularly. Irregular breathing could be a sign of distress. 
• The fish seem to enjoy eating.
• They swim energetically and freely around the tank.
• A healthy and happy fish has glowy skin. For humans, the skin is a reflection of your inner health, and the same can be said for fish. 
• They are active members of their aquarium community. An unhappy, fearful fish tends to stay away from other fish.

44. Do Fish Swim Up and Down?

Most fish do not swim up and down. Instead, they sink or rise in the water, much like a hot-air balloon or a helium-filled balloon sinks and floats in the air. 

45. How Do Fish Schools Form?

Schools form through a phenomenon called self-organizing. These schools have no leaders and remain intact by the “zone of repulsion” instinct that kicks in when fish encounter their neighbors. 

46. Fish Tornado

A fish tornado is a rapid and swirling motion created when large groups of fish swim together and around each other at high speeds. Not sure why they’d do this, but it seems like fun.

47. Are Fish Smelly?

Fish aren’t smelly while submerged in water; just after you catch them, they would smell like lake water or the ocean. The stinky odor sets in after you’ve killed a fish, similar to any other dead and decaying animal.  

48. Not All Fish Lay Eggs

There are a handful of fish that do not lay eggs to reproduce. Instead, these fish give birth to live babies, known as fry– how cute? 

49. The Oldest Fish We Know 

The oldest recorded fish on earth is the Australian lungfish, which reached its 65th year of age. This means that this particular fish has been around since the Soviet Union inaugurated the “Space Age.”  

50. Fish Don’t Really Sleep Like Humans

Fish do not sleep the same way as mammals; rather, most fish rest. They will slow down their activity and metabolism while remaining alert. They’ll find a secure spot or nest or simply float in place to rest.  

51. Fish Have Exquisite Taste

Fish can distinguish different flavor profiles such as sweet, sour, bitter, and salty. Much like humans, their taste buds do not end with their tongues. Fish have taste buds expanding to other parts of their body, including the rest of their mouth, the outside of their body, and fins. How’s that for a tasty fish fact?  

52. Saltwater Fish Are Thirstier

It’s pretty evident that salt water contains way more salt than freshwater. So the fact that saltwater fish are thirstier comes as no surprise. How this works is that fish have to filter way more water to get rid of the high salt content and so will gulp in water to stay hydrated. 

53. Your Lipstick Likely Contains Fish Scales

This might sound gross, but with a little more research on cosmetic ingredients, you’ll find that fish scales in your makeup are not that bad. Cosmetologists add this scaly ingredient to their cosmetics, such as eye-shadow, lipsticks, and nail polish for shimmer and shine. 

54. How To Tell the Age of A Fish

You can tell a fish’s age by looking at the calcified or hardened structures of its bodies. These hard structures form rings around the fish according to its seasonal growth. By counting these rings, you’ll be able to tell a fish’s age.   

55. Fish Cannot Chew As Mammals Do

If a fish had to chew and grind food with their teeth the way we do, they’d undoubtedly risk their lives. A fish cannot chew and obtain oxygen at the same time. Some fish similarly grind their food like humans, while bottom feeders tend to crush shellfish before eating them. 

Also, sharks seize and hold their prey using their sharp teeth and then swallow it whole– scary indeed.   

56. The Fastest Fish in the World

The fastest fish in the world right now is the black marlin, which can swim at speeds from 65 miles to 80 miles per hour. The sailfish isn’t too far beyond, though, with a swimming speed between 62 – 68 miles per hour. 

57. Not All Fish Have Scales

It’s pretty hard to believe that not all fish have scales, but low and behold, many fishes are scaleless. Clingfishes, lampreys, hagfishes, and most eels are free from scales. 

58. You Won’t Believe How Slow the Slowest Fish Is

The slowest fish on earth is the tiny dwarf seahorse that lives on the Bahamas coast. The dwarf seahorse can only swim up to 5 feet per hour. 

59. The Ugliest Fish To Exist

The blobfish has earned the title of ugliest fish in the sea. In fact, it is so ugly that it’s also been voted the ugliest animal on earth. It’s no wonder the blobfish spends its life in the ocean’s depths, and we rarely get a glimpse of it. 

Not to hurt blobfish’s feelings- but after seeing one, you’ll understand why it earned this title.  

60. The Biggest Fish Ever Caught?

The largest fish ever caught by man is a hefty 2,664-pound great white. This mid-blowing catch happened off the coast of Australia in 1959 by angler Alfred Dean. It took him only 50 minutes to reel in the massive one-ton shark.   

61. The Mudskipper, Not Your Ordinary Fish 

The mudskipper probably has some of the craziest abilities of all fish. This fish crawls and skips on mud with leaps of up to two feet. If skipping across muddy surfaces is not enough, this daredevil fish can also climb trees and low branches. Who said fish couldn’t be pro-athletes? 

62. There’s a Four-Eyed Fish

The ocean has a fair share of creepy critters, so a four-eyed fish makes complete sense. Belonging to the genus Anableps, there are two species of tropical American fish that use four eyes above and below water at the same time. 

63. Salmon Are Highly Adaptable

Salmon is known as a highly adaptive and persevering fish. They can live in both salt and freshwater and often migrate great distances from the sea to rivers. They even swim up rivers while battling strong currents and rapids in order to reproduce in clean, fresh water.  

64. There’s a Tail-Less Fish

The ocean sunfish (also called Mola mola) do not have tails. This rare species looks like it has one giant head with two fins. This oddly-shaped fish swims using its fins and would often float on one side. How’s that for an interesting fishtail? 

65. More People Fish Than Play Golf in the US

The number of people that fish is about double and triple the number of golfers and tennis players respectively. 

66. Fish Are Expert Sex Switchers

When in desperate and dire situations, some fish can change their sex. Some species can also make the sex switch whenever they desire. Known as sequential hermaphrodites, the fish switches sex permanently at some point in their lives. 

67. The Three Main Fish Groups

There are three main fish groups that all species in the ocean are subdivided into, namely:

• Superclass Agnatha— the jawless fishes
• Chondrichthyes class– cartilaginous fishes
• Superclass Osteichthyes– bony fishes

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