5 fascinating facts about sharks – CNN

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While these best deep blue hunters evolved to survive cold, dark climates, sharks are no match for the ultimate predator: humans.

That’s why Shark Week, which runs July 11-18, was launched 33 years ago by the Discovery Channel to encourage shark conservation and educate the public about these underwater predators.

Of the 31 oceanic species of sharks and rays, 24, or more than three-quarters, are now threatened with extinction due to their sharp decline in numbers, according to the study.

With Hollywood blockbusters like “Jaws” and “The Meg” stoking the flames of fear and paranoia in humans, these underwater animals suffered from a serious image problem.

However, sharks play a crucial role in their environment and control the animal kingdom.

The hammerhead shark population in the Sea of ​​Cortez, between Baja California and mainland Mexico, has declined sharply due to overfishing.

Sharks balance the food chain

As sharks have been killed due to overfishing in the Sea of ​​Cortez, located between Baja California and mainland Mexico, other creatures have rushed to take their place in the food chain.

Wahoo and hammerhead sharks, as well as other fish species such as marlin and swordfish, have seen a sharp decline in their populations due to commercial and local fishing in the area.

Scientists believe the decline of sharks is one of the reasons Humboldt squid are now living in greater numbers in the Baja. The creature can grow up to 7 feet (2.1 meters) long and weigh over 100 pounds (45.4 kilograms).

Squids only live a few years, but they reproduce much faster than sharks.

Some sharks are partially warm-blooded

Although they have a reputation for being cold-blooded, some sharks – like the great white shark and the salmon shark – are able to regulate their temperature internally, according to a June study published by the British Ecological Society.
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The study found that endothermic fish, able to regulate their own body temperature, swam one and a half times faster than ectotherms, animals that depend on the outside temperature to regulate their body heat.

The researchers couldn’t draw any conclusions about how warm blood might be of use to sharks, but they speculated that it might help them when foraging or migrating.

Sharks can live for hundreds of years

Sharks tend to have one of the longest lifespans of creatures in the animal kingdom.

Using radiocarbon dating to estimate the age of Greenland sharks for a 2016 study, researchers found that the underwater creatures lived at least 272 years, with the largest of the group being around 392 years old.

Animals do not reach maturity until they reach the ripe age of 150, and they are the oldest vertebrates known to man.

Some may glow in the dark

A small number of sharks are bioluminescent and glow hundreds of feet below the ocean’s surface, according to a February study published in Frontiers in Marine Science.
One of the sharks is the kite shark (Dalatias licha), which stretches almost 1.8 meters. It is also the largest known bioluminescent shark in the world.

Very little is known about glow sharks because sharks mostly roam the deep waters, which begin more than 200 meters below the ocean’s surface.

The researchers also found that the southern lantern shark (Etmopterus granulosus) and the black-bellied lantern shark (Etmopterus lucifer) have bioluminescent abilities.

They almost disappeared millions of years ago

Despite having a reputation for being a top predator, sharks died at an alarming rate millions of years ago.

More than 90% of deep-sea sharks disappeared from the planet around 19 million years ago, scientists say.

The researchers said they could not confirm the cause of the mass extinction event, and that it could have lasted from a single day to 100,000 years.

Based on current research, there have been no climate or ecosystem crises during this period, leaving a gaping knowledge hole for scientists to do more research and unravel the mystery.

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