Surprising shark facts

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The sight of a pointed dorsal fin slicing through the waves strikes many with a feeling of primal, blood-freezing fear. Sharks have a fearsome reputation stretching back much further than the iconic 1970s film Jaws but, for many of us, the reputation is undeserved.

In fact, sharks are actually under threat from man. Whether caught for their fins, to be served in fish and chip shops or as accidental bycatch it’s clear that shark numbers are falling. To help you understand the beauty of the sharks residing in UK waters, here are seven surprising facts.

1. Around 21 species live off the UK coast.

According to the Shark Trust you’re most likely to meet the basking shark. These plankton-eating gentle giants can grow up to 11 metres and are seen off Britain’s west coast throughout the summer. If you’re lucky enough to see one of these protected animals, please report your sighting to The Shark Trust’s basking shark project.

Anglers meanwhile are most likely to catch catsharks and in the South West they have been helping to track their movements through tagging.

2. A shark’s skeleton is made out of cartilage like your nose or ear.

A cartilage skeleton is much more flexible than bone and also lighter. Shark body tissue however is heavier than water meaning they must keep swimming to stay afloat.

3. Sharks don’t sleep.

There is some controversy surrounding this statement as scientists still work to fully understand sleep in many animals. We do know however that sharks need to constantly move oxygen-rich water over their gills in order to breathe and for most this means continually swimming. Instead of a deep sleep like we have sharks are thought to have active and restful periods.

4. Shark skin is covered in tiny teeth.

These teeth or denticles face backwards, reducing turbulence in the water so that sharks can swim faster. If you stroked a shark you would find their skin smooth in one direction and rough in the other.

5. Sharks have to be relatively old before they can reproduce.

The spiny dogfish for example doesn’t reach sexual maturity until it is 12 years old and the gestation period of its pups is a staggering 22 months. These factors can make sharks very vulnerable. When they are caught or killed before they can reproduce it results in dramatic population decline.

6. Sharks have a conveyor belt of teeth.

Shark teeth are larger versions of the denticles covering their skin and depending on their diet, they can wear out quickly. To solve this problem sharks have several rows of teeth that work like a conveyor belt. New teeth grow through as replacements and move forward in the mouth around every two weeks depending on the species.

7. Sharks can have up to eight fins.

Depending on species a shark may have: a first and second dorsal fin, pectoral fins and pelvic fins on each side, an anal fin, and a caudal (or tail) fin. These fins help them to balance, steer and move through to the water. The dorsal fin of particular species is prized for the Chinese delicacy of shark fin soup. Wildlife conservationists highlight this as the main reason for the global decline in shark numbers.

How you can help.

Unfortunately, the number of sharks in our seas is falling but you can help them out with a simple bit of beachcombing as part of The Great Eggcase Hunt.

Some species of shark, ray and skate lay leathery eggcases, also known as mermaid’s purses, on the sea bed. Each of these cases contains an embryo that grows into a perfect miniature of its parent.

If you see an eggcase at the beach, the Shark Trust would love to hear from you. Your data can help them plot where shark, ray and skate nurseries are in order to better protect these animals. If you want to know what kind of eggcase you’ve found consult The Shark Trust’s ID guide.

Source: bbc.co.uk