65 Interesting Facts About Fish

  1. Fish are fully aquatic vertebrate animals that breathe underwater. They use gills for breathing, fins for locomotion, and scales to protect their bodies.
  2. There are three main types of fish: jawless fish (hagfish, lampreys), cartilaginous fish (whale shark, great white shark, skates), and bony fish (tuna, cod, lionfish, sea horses).
  3. There are more than 30,000 species of fish in both saltwater and freshwater. Around 20,000 species are bony fish.
  4. The first fish on earth lived more than 500 million years ago. This first true vertebrate was 6 cm long and had external gills and large protruding eyes. (Source)
  5. Catfish have the highest number of taste buds in the animal kingdom. Few large catfish can have up to 175,000 taste buds. It helps them to detect prey in extremely muddy and murky water. Comparatively, humans have 10,000 and chickens 24 taste buds. (Source)
  6. Few fish species live in the Antarctic Ocean. The temperature of the Southern Ocean is lower than the minimum temperature required for the survival of any fish. But these unique fish can survive thanks to excellent antifreeze proteins in their bodies, which work better than any household antifreeze. (Source)
  7. Pupfish are known as the “hottest fish in the world.” These fish can live in waters with temperatures of 114 F (45.5 C).
  8. Apart from sharks, other fish don’t have eyelids. These fish have transparent eyelids that help them focus on various objects in the water.
  9. The giant guitarfish can retract its eyeballs 1.6 inches inside its head in the absence of eyelids. They need this to protect their eyes from sand or coral on the bottom of the sea while hunting. Few other animals also have this feature but can’t retract their eyeballs this far. (Source)
  10. The lingcod is an omnivorous and cannibal fish that has more than 500 teeth in its mouth. This aggressive fish can lose and re-grow 20 teeth every day. (Source)
  11. Sloan’s viperfish has the largest teeth relative to its head size among fish. The head of this fish is 2 cm (0.8 in), and its teeth are more than half of the head’s length. (Source)
  12. The common fangtooth has the largest teeth of all marine species relative to its body size. These sharp teeth help this fish to eat an animal one-third of its size. (Source)
  13. Red-bellied piranhas have the strongest jaws and sharpest teeth among fish.
  14. Megalodon is the largest known fish and marine predator ever existed on earth. The average length of this shark was 10.2 meters (33.5 feet), and the largest ever measured was 17.9 meters (58.7 feet) long. According to estimates, their maximum length could be 25 meters (82 feet). Their estimated weight is between 30 to 65 metric tons (143,000 lb). (Source)
  15. The whale shark is the largest fish species that can reach over 40 feet in length and has more than 20 metric tons of weight. The Whale shark is also the largest non-mammalian vertebrate on earth.
  16. Paedocypris progenetica is the world’s smallest fish and vertebrate. It is present in Southeast Asia. The size of its fully mature female is just 7.9mm (0.31 inches). (Source)
    A small fish on human hand
    World's smallest fish is also the smallest vertebrate animal

  17. The world’s largest freshwater fish is the beluga sturgeon. Its length is up to 26 ft (8 m) and can attain a weight of 2,000 kg (2 metric tons). These fish can live for more than 100 years. (Source)
  18. There are 60 species of batfish. This fish uses its fins to walk at the bottom of the deep sea instead of swimming. (Source)
  19. At least 11 species of fish can walk on land. So far, the cave angelfish is the only extant species observed walking on land. (Source)
  20. Few parrotfish and wrasse species use their mucus to build a protective layer around their bodies before sleeping every night. According to estimates, these mucus cocoons protect these fishes from predators, parasites, dust, and DNA damage from sunlight. (Source)
  21. Whales (blue whale, sperm whale, killer whale, etc.), dolphins, and porpoises look like fish. However, they are marine mammals.
  22. Starfish, jellyfish, shellfish, crayfish, and cuttlefish are also not among fish despite their fish-related names.
  23. Few species of fish can change their color. The slow color change happens during different stages of life. The fast color change is the result of stress and camouflage. (Source)
  24. Several species of fish have different shades of color on top and bottom. These fishes are darker at the top and relatively lighter in appearance at the bottom.
  25. Numerous instances of fish falling from the skies, commonly known as “fish rain,” have been observed. It happens when waterspouts suck fish and other animals from a lake or ocean and later throw them back to the ground after a decrease in wind speed. (Source)
  26. The tan bristlemouth is known as the most abundant vertebrate on earth. This small fish lives in the mesopelagic zone (200 to 1,000 m deep) in the ocean. (Source)
  27. Fish constitute more than 50% of venomous vertebrates. Lionfish, stonefish, and scorpionfish are the most venomous fish, while stingrays cause the most marine injuries. (Source)
  28. The stonefish are the most venomous fish, while the estuarine stonefish have the largest venom gland. The most poisonous fish are the pufferfish due to the presence of tetrodotoxin, a powerful non-proteinous poison, in their bodies. (Source)
  29. Fish have a special sensory system known as the lateral line. This system contains hundreds of neuromast, a sensory structure, spread over the fish’s head, trunk, and tail fin. This system assists fish in detecting motion and pressure in the water. (Source)
  30. Grouper, wrasse, and a few other fish are born female. They can change their gender to male after achieving sexual maturity. (Source)
  31. Few fish species can move backward in different locomotion. These include electric eel, triggerfish, black ghost knife fish, etc.
  32. Species of cusk eel (Abyssobrotula galatheae) can live in the depth of 8,370 m (27,460 ft) underwater. It is the maximum depth possible for any fish to live. (Source
    Cusk eel
    Cusk eel can live at maximum possible depth for any fish

  33. Electric eels can generate an electric charge of 600 volts. Multiple shocks can cause death in humans due to respiratory or heart failure.
  34. Greenland sharks can live for more than 300 years, the longest lifespan of any vertebrate animal. This shark achieves sexual maturity at the age of around 150 years. (Source)
  35. The longest-living freshwater bony fish is the bigmouth buffalo. A female bigmouth buffalo fish was 112 years old in 2019. (Source)
  36. The Gulf corvina is the loudest known fish on earth. These fish can produce sounds of 202 dB that can even damage human ears. (Source)
  37. Most fish release their eggs and sperm into the ocean. However, few fishes like sharks, rays, and chimeras provide better protection to their newborns after internal fertilization. Their eggs are wrapped into egg cases and are commonly known as mermaid purses. (Source)
  38. Sailfish are considered the fastest fish in the ocean. This fish can swim at a speed of 68 mph or above. (Source)
  39. The five fastest animals in oceans are fish. These are sailfish, swordfish, marlin, yellowfin tuna, and bluefin tuna. There are 8 fish on the list of the 10 fastest animals in the ocean. (Source)
  40. Sea horses are the slowest marine fish due to their erect posture while swimming. The fastest speed of the dwarf sea horse is 0.016 km/h (0.001 mph). (Source)
  41. The male seahorse has a pouch attached to the front side of its tail. The female seahorse deposits eggs in this pouch where the eggs hatch.
  42. Tilefish, Swordfish, and Shark have a high amount of mercury in their bodies. Therefore, it is unsafe to eat these fish in large quantities.
  43. Finfish have the lowest amount of sodium in seafood. Finfish include commonly consumed fish like cod, tuna, salmon, halibut, catfish, etc. (Source)
  44. Fugu or blowfish is a delicacy in Japan. This dangerous fish is more poisonous than cyanide. (Source)
  45. The northern giant seadevil, an anglerfish, has the largest sexual dimorphism in the animal kingdom. Females in this species can be 60 times longer and 500,000 times heavier than mature males. (Source)
  46. Most fishes have scales that protect their bodies. Scales also provide information about the age and growth of a fish. But there are scaleless fish too. These include clingfish (over 150 species), scaleless dragonfish (over 180 species), and others.
  47. Few lipsticks and other shimmery makeup contain fish scales. These scales give them a glow due to their pearly quality. (Source)
  48. Fish are cold-blooded animals that change their body temperature according to their environment. But few species of tuna and sharks can warm the core of their bodies compared to their surroundings. These warm-blooded fish can swim faster and farther than their cold-blooded counterparts. (Source)
  49. Damselfish can perfectly see ultraviolet (UV) light. Few other fish can also see UV light, but their vision is blurry. Damselfish uses this ability to identify its enemies. (Source
    A damselfish in water
    Damselfish has the perfect UV vision among fish

  50. Freshwater fish can see infrared light by converting Vitamin A1 to Vitamin A2. It helps them to see better in murky waters. (Source)
  51. Goldfish have highly developed vision. They are the only animals that can see both infrared and UV lights. (Source)
  52. four-eyed fish has two large eyes divided into two parts. These fish swim along the surface of the water with the upper part of the eyes in the air and the lower in the water. The top half of these eyes are sensitive to green, while the lower part is sensitive to yellow. Both these parts are responsive to blue, violet, and ultraviolet lights. It makes it easier for them to see clearly in and outside the water simultaneously. (Source)
  53. According to previous speculations, the Hagfish, a jawless fish, is the only known living animal having a skull without a vertebral column. But research has proved that this last common ancestor of vertebrates also possesses a vertebral column. (Source)
  54. Fish can suffocate inside water if there is less than necessary oxygen. Algae and aquatic plants are the main sources of oxygen in water.
  55. Unlike mammals, many fish can produce gadusol in their bodies. This compound protects them against UV radiation. It is the reason they don’t get sunburn. (Source)
  56. Few fish species like trout, char, and salmon can get deadly sunburn due to a low amount of protective pigment in their skin. The problem can aggravate if they are swimming in ultra-clear water. (Source)
  57. Flying fish can achieve a height of over 4 feet in the air up to a distance of 655 feet in a single glide. This fish can take its flying distance up to 1,312 feet before fully returning to the water. (Source
    Flying fish gliding on water
    Flying fish remain at 4 feet high for a distance of 655 feet

  58. The Ocean sunfish (also called mola) is the world’s heaviest bony fish at around 5,000 pounds weigh. It is also known for producing the most number of eggs. The fish can release an estimated 300 million eggs in a season. Even then, the fish is listed as vulnerable by IUCN. 
  59. The three-spined toadfish is the only fish that can cry. Its voice of crying is similar to that of a crying baby. (Source)
  60. Fish communicate with each other by using sound, smell, body language, electric impulses, etc. (Source)
  61. A study proves that fish also have feelings. They emotionally respond to changes in their environment. (Source)
  62. There is a common belief that fish have a very short memory. But studies on captive and wild fish have proved they are intelligent with long memories. (Source)
  63. Most of the fish species either live in marine or freshwater habitats due to their management of salts. But few fish species can survive both types of environments. These anadromous fish include salmons and a few species of sturgeon. (Source)
  64. Several fish species migrate to different parts of the ocean and other water bodies. They can be divided into three types. Oceanodromous fish (e.g. herring) migrate from one place in the sea to another. Anadromous fish (salmon and a few others) live in the sea but migrate to fresh water for breeding. Catadromous fish (several eel species) live in the freshwater and migrate to the sea for breeding.
  65. The male cardinalfish, native to the Banggai islands of Indonesia, broods eggs and the young in its mouth.


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