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Some sharks have to constantly swim in order to breathe

 

Photo by Elias Levy licensed CC BY 2.0

There are more than 400 types of sharks in the world’s oceans. These fish are often thought of as fierce creatures that attack humans. But the truth is most attacks happen because a shark mistakes a swimmer for its prey. In fact, you’re more likely to be struck by lightning than injured by a shark. And get this: many more sharks are harmed by humans every year than the number of people harmed by sharks.    

July 14 is Shark Awareness Day. That makes it a great time to learn more about these cool creatures. Here’s Mr. Orlando with some amazing shark facts.

Whale shark
Photo by Justin Henry licensed CC BY 2.0

The whale shark is the longest shark in the world and biggest fish on the planet, measuring in at about 10 metres long — the same size as a school bus! While it’s supersized, the whale shark doesn’t go after big prey. Instead, it opens its mouth and filters food from the water, like shrimp, fish eggs and algae.

As for the smallest shark, that’s the dwarf lanternshark — it's smaller than a grown-up’s hand! It lives in deep, dark parts of the ocean, so it’s rarely seen.

 

Sharks have many rows of teeth.
Photo by fredrik Andreasson licensed CC BY 2.0

Most sharks have many rows of teeth — the front row is called the “working” row, and these are the shark’s largest teeth. The second row is smaller than the first, and the third row is smaller than the second, and so on. These teeth fall out or break off pretty easily, but that’s no worry for the shark. When a tooth falls out, a new one from the row behind moves forward to take the spot of the one that was lost. Since this happens so often, a shark can have over 30,000 teeth during its lifetime!

 

Shark skin feels like sandpaper
Photo by Pete Sheffield licensed CC BY-SA 2.0

Sharks are covered in scales called dermal denticles, which are scales that are covered with a layer of enamel, like our teeth. The denticles protect the shark’s skin from injury. They also help water glide over the shark as it swims so it can move quickly and quietly through the ocean.

 

Sharks can hide in the ocean
Photo by Elias Levy licensed CC BY 2.0

Forget about playing hide-and-seek with a shark — it’ll probably win. A shark’s skin helps it hide from prey and predators. The upper part of a shark’s body is dark, which makes it hard to see from above because it blends in with the dark ocean. The bottom of a shark is lightly coloured. From below, the light skin of the shark looks like sunlight shining through the ocean’s surface so both predators and prey often don’t notice a shark even if it’s in plain sight.

 

Some sharks have to constantly have to swim forward to stay alive.
Photo by Niall Kennedy licensed CC BY-NC 2.0

For some sharks, like the great white and the mako, there’s no time to stop swimming. They have to keep on the move to stay alive. All sharks take oxygen from water so they can breathe. But sharks like these ones can’t pump water over their gills. So to stay alive, the sharks have to constantly swim forward. This keeps water filtering through their gills, so they’re always taking in oxygen to breathe.


Canada Post is celebrates sharks in Canadian waters

Shark stamps
Images courtesy of Canada Post

Out of the 400 sharks that live in the world's oceans, there's only 30 that are native to Canadian waters or known to visit our shores. To honour the sharks, Canada Post has chosen five species to be highlighted on their new stamps.

Beginning at the top left, they are the shortfin mako (isurus oxyrinchus), basking shark (cetorhinus maximus), white shark (carcharodon carcharias), Greenland shark (omniosus microcephalus) and the blue shark (prionace glauca).


Want to read more about sharks? Check out 6 facts about the longest-living, slow-swimming Greenland shark