50+ Interesting Facts About Sharks

1. Sharks are cartilaginous fishes, closely related to rays and skates. There are more than 400 species of sharks.
2. Of these hundreds of shark species, only four attack humans without provocation. These are great white sharks, tiger sharks, bull sharks, and oceanic whitetip sharks.
3. Scientists have discovered three shark species that glow in the dark. These include the kitefin shark, blackbelly lanternshark, and southern lanternshark. Thousands of photophores in the skin of these shark species provide this unique feature that is important for camouflage. (Source)
4. A warming system for the brain and eyes is present in mako and porbeagle sharks. This system keeps the temperature higher in the brain and eyes of these sharks compared to their surroundings. It protects their nervous system and improves the visual sensitivity. (Source)
5. Among all the shark species, the bull shark has the strongest bite related to its body size. It is primarily due to its wide head and jaws. (Source)
6. According to a study, prehistoric great white sharks had the strongest bite among all the animals in history. This study proves that the bite of this marine animal was even more powerful than that of the T.rex dinosaur. (Source)
7. According to a study on grey reef sharks, the diving behavior of sharks is affected by the moon, season, and time of the day. Sharks dive deeper during a full moon, spring season, and in the morning. On the other hand, these sharks move to shallow water on a new moon and during the winter season. (Source)
8. The whale shark is not only the largest shark but also the largest fish species. It can gain a maximum weight of 21.5 metric tons and a length of 12.65 m (41.5 ft.).
9. The lifespan of whale sharks is between 100 and 150 years, the longest among all the shark species.
10. Most sharks are big and heavy, but there are smaller sharks too. The smallest among these is the dwarf lanternshark, with a length of fewer than 8 inches.
11. A Greenland shark is known to be the world’s longest-living vertebrate. According to estimates, it was up to 512 years old in 2019. (Source)
12. The shark is the only fish that cannot swim backward. Pulling it in reverse can result in the death of a shark due to interference in its respiratory process. (Source)
13. It is a misconception that sharks do not suffer from cancer and that their cartilage can cure cancer. Scientists have found cancer in at least 23 species of sharks. (Source)
14. The gestation period of frilled sharks is 42 months, the longest known gestation period of any animal. The reason behind this long pregnancy is the intense cold of the deep-sea habitat that slows metabolic processes. (Source)
15. Few female shark species (blacktip and hammerhead sharks) can reproduce without mating with any male shark. (Source)
16. Sharks reproduce through internal fertilization, which is different from external fertilization in other fish. They are either oviparous (lay fertilized eggs), viviparous (produce live births), or ovoviviparous (eggs develop inside the body without a placenta). After birth, the pups quickly swim away from other sharks, including their mothers, to protect their lives. (Source)
17. Few shark species become immobile when upside down. This state, known as tonic immobility, starts 60 seconds after their upside-down position and may continue for 15 minutes. Common sharks that go into this state include tiger sharks, lemon sharks, sandbar sharks, blacktip reef sharks, whitetip reef sharks, and silky sharks. (Source)
18. The shortfin mako shark is the fastest shark and one of the fastest fish. It can swim at a speed of up to 46 mph. (Source)

    

    Shortfin mako is the fastest shark and one of the fastest fish

    
    
19. The slowest shark is the Greenland shark, with a top speed of just 1.7 mph. According to estimates, the cold water of the Arctic Ocean is the reason behind the slow movement of these sharks. (Source)
20. Sharks in aquariums do not eat smaller fish. It is due to their learning of a feeding technique known as target feeding. The shark knows the food it is allowed to eat and refrains from “prohibited” food. (Source)
21. Few sharks eat the eggs of their siblings when they are in their mother’s womb. This sibling cannibalism is present in species such as great white sharks, tiger sharks, Greenland sharks, Mako sharks, and a few other species.
22. Like turtles and salmons, female lemon sharks also return to their birthplace to give birth to their pups. This strange behavior of the yellow-colored fish was discovered after a 19-year-long study. (Source)
23. Sharks provide several benefits to the aquatic environment directly and indirectly. They enhance reproduction in healthy fish by eating sick or injured fish. These fearsome creatures protect seagrass from turtles and coral reefs from herbivorous fish. They also indirectly reduce carbon in the atmosphere by protecting seagrass meadows.
24. Shark ecotourism is a profitable industry with an annual worth of more than $300 million globally. It is also creating 10,000 jobs directly. (Source)
25. Sharks managed to survive five mass extinction events. They are diverse creatures that can live in different parts of oceans and also in freshwater. It is considered a significant feature that played a major role in the survival of sharks during these mass extinctions.
26. Sharks or shark-like fish initially appeared on earth around 450 million years ago. The oldest discovered shark teeth are 410 million years old, while the first recognizable sharks are 380 million years old.
27. In sharks, growth rings are formed on vertebrae yearly. Therefore, these rings are helpful in determining the age of this fish.
28. Female sharks are usually larger in most shark species that reproduce live births. On the other hand, males and females are either of similar size or males slightly larger than females in egg-laying sharks.
29. The shark with the deepest dwelling is the goblin shark that lives in underwater mountain ranges and outer continental shelves.
30. There are several migration patterns in sharks. Few species do not migrate at all, including bonnethead sharks, nurse sharks, etc. Some shark species migrate for shorter distances. Tiger sharks, sandbar sharks, and oceanic blacktip sharks are examples of such sharks. Few species, like blue sharks and mako sharks, migrate for long distances.
31. The only whale that kills and eats sharks is the killer whale. These marine mammals can hunt all types of sharks, including makos, great white, whale sharks, etc.
32. Sharks are more likely to attack males than females. Sharks target 84% of men during their attack on humans, while around 89% of fatalities of shark attacks are males. (Source)
33. It is a myth that sharks can smell a drop of blood in the water from a mile away. Sharks can smell blood at a maximum of one part per 10 billion. (Source)
34. A few relatively smaller animals can also eat sharks. Alligators can kill and eat a few species of sharks if they enter their territory. (Source)
35. Sharks kill around ten human beings annually, while humans kill more than 100 million sharks during the same period.
36. The most important reason for such a high number of shark hunting is the “shark fin soup,” a delicacy in several Southeast Asian countries. Only the fins of sharks are used for this soup, while the remaining shark is usually discarded.

    

    Sharks are mostly hunted for their fins
    
    

37. Sharks are also known to attack and kill far bigger animals. At least one such successful encounter between sharks and the calf of a humpback whale has been seen. (Source)
38. Most sharks cannot remain alive without motion. Swimming keeps the water moving to their gills which is necessary for their life.
39. Most sharks live in oceans and seas. However, river sharks and bull sharks can swim in freshwater habitats: rivers, bays, etc.
40. Whale sharks, basking sharks, and megamouth sharks are the three largest shark species. All these sharks are filter-feeders that eat plankton and other small marine animals.
41. The basking shark is the second biggest shark, with a length and weight of up to 11 m (36 ft.) and 7 tons. It has an enormous liver that can weigh up to one ton and provides up to 400 gallons of liver oil. (Source)
42. Sharks are cartilaginous fish without bones. Cartilage is lighter and more flexible than true bones. It helps them to swim faster and take sharp turns.
43. Sharks have a monochromatic vision and only see in black and white. However, they have excellent visual acuity that assists in focusing images to 15 meters or more. Sharks in deep water and shallow water have different eye structures to adjust the light sensitivity accordingly. The Tapetum lucidum in their eyes increases low-light vision. (Source)
44. Sharks are known for their excellent electroreception qualities. There are hundreds of electroreceptors or ampulla of Lorenzini (jelly-like tubes) inside a shark’s skin on the head. Sharks can detect the earth’s electromagnetic field and the minute electric potentials from the prey’s muscle contraction using this electroreception. It assists sharks in migration and hunting.
45. Shark's skin has a very rough texture due to its teeth-like structure. It is the reason behind using the shark’s skin as sandpaper.
46. All shark species have teeth. Various species use these teeth for cutting, grabbing, grinding, and hooking their prey. Sharks have several rows of teeth in their jaws and can replace a fallen tooth with a new one even in a day. A lemon shark can shed 30,000 teeth in its lifespan. (Source)
47. Shortfin mako sharks can leap up to 20 feet out of water when in danger. Despite their defensive techniques like speed and long jumps, they are classified as vulnerable by IUCN. (Source)
48. Sharks have excellent senses of hearing, touch, electroreception, and lateral line. These senses help these animals in their hunting.
49. In most animals, the upper jaw is attached to the skull, while the lower jaw moves freely. But in sharks, both jaws can be detached when they hunt. It makes it easier for them to catch prey.  
50. Sharks cannot make sounds due to the absence of vocal cords. They communicate by using body language.
51. Like other fish, sharks also have less-developed brain sections related to feeling compared to mammals. They cannot smile due to their rigid jaws.
52. The cookiecutter shark is a small deep-water fish. It gets the name due to its feeding habit. This shark attaches itself to the much larger prey and cuts a perfectly circular chunk of its flesh.