Blue sharks are to be found in every ocean and sea in the world, having the widest distribution of any shark species.
Members of the requiem shark family, they are classed as near threatened on the endangered species list, which is a misnomer if every I heard one.
All ‘near threatened’ means is that their numbers appear to have gone down in some parts of the world, though not necessarily in others.
Widespread studies are only now being carried out into shark behaviour and patterns, largely due to the invention and affordability of satellite technology, that allows sharks to be caught and tagged, and for monitoring stations to be planted on the sea bed to allow scientists to collate data.
While it is true that sharks are being fished to extinction, largely for that Chinese delicacy, shark’s fin soup, the actual numbers of most shark species have not been determined.
Blue sharks like swimming in cooler waters. While in the North Atlantic they are to be found swimming near the surface, in the tropical Indian or Pacific Oceans, they may be found at depths of 350 metres (over 1,000 feet).
Blue sharks are so widely distributed; they are to be found in the waters off every continent except Antarctica.
They tend to stay in deeper waters and not approach shorelines, unless there is an underwater continental shelf close to shore, as in the Red Sea.
Are blue sharks dangerous?
Blue sharks are shy and nervous around people. Should you ever come face to face with a blue shark, any sudden movement on your behalf with see it shoot off into the darkness of the surrounding ocean.
Despite claims to the contrary, there have been no known reports of blue sharks attacking humans without provocation.
Check for yourself on the International Shark Attack files.
The only people who have been injured by blue sharks are fishermen and divers who attempted to spear and kill one.
When trapped, the blue shark will fight to the death. Even an apparently dead blue shark on a boat’s deck can whip its head round like lightning and bite the hand that touched it.
That is another weapon in their armoury. They can play dead too, so that your guard is down, then strike when you least expect it.
Unfortunately, beautiful blue sharks are frequently the target of sports fishermen who get their kicks from baiting and then hooking large sea creatures and reeling them in and out until the poor animal is exhausted and can finally be reeled on board.
Blue sharks are fish by the way, but in this case can be called animal, (as in animal, vegetable or mineral).
Blue sharks ride the oceanic currents
Blue sharks are slow swimmers normally, but can put in bursts of speed when the situation requires it.
Did you ever watch the film Finding Nemo?
Do you remember how, in the movie, large tea turtles saved Marlin and Dory as they were riding the East Australian Current?
This is exactly what blue sharks spend their time doing. To the north of the equator, sea currents move west to east, and in the southern hemisphere, east to west.
Blue sharks must be thrill-seekers because this is how they travel round the world. They just climb on board, chill out and enjoy the ride!
Of course, this could be considered a form of relief for the blue shark, because as a species they are plagued by parasites that they can’t knock off.
Riding the major oceanic currents may well relieve the itchiness of parasitic infection, if it doesn’t actually knock them off.
Because short film about blue sharks getting caught and tagged
- Shark Cannibalism and Early Life: Saltwater Fish: Animal Planet
Shark cannibalism happens in the womb, usually with sand tiger sharks. Read more about shark cannibalism and why shark cannibalism occurs.
- Blue Shark Nursery
NASA website carries details of blue shark nursery in Atlantic Ocean near Brazil.
- Blue shark - Wikipedia, the free encyclopedia
Details as they are known about the blue shark, its habitat, ecology, reproduction and relationships with humans.
- FLMNH Ichthyology Department: Blue Shark
Florida Museum of Natural History Ichthyology Department. This page contains educational sections about the biology, ecology and conservation of the Blue Shark.
Blue sharks' life span and reproductive cycle
Blue sharks can grow to 12 feet long, and sometimes even bigger, but are generally around 4’ to 6’ in length. It is said they can live for 30 years, but we will know better in future thanks to studies being carried out now.
- Female blue sharks reach sexual maturity at just 4 to 5 years old, which is exceptionally young for a shark.
- Most sharks follow a similar pattern to humans, not maturing until they are in their teens at least.
- Their pregnancies last for between 9 and 12 months, a figure which no doubt we will know exactly, one day soon.
- Blue sharks are viviparous, meaning the eggs hatch in utero and the baby sharks are fed by a placental yolk sac, unlike many other species of shark who don’t provide nourishment at all, leaving the baby sharks, pups as they are known, to eat each other to survive.
- Blue sharks commonly have litters of between 25 and 50 pups, but have been known to have as few as 4 and as many as 135.
- They also give birth in nursery areas, normally warmer coastal waters where few predators live, giving the pups the greatest chance of survival.
One such known site in the south western Atlantic Ocean, near the southern coast of Brazil. There, juvenile blue sharks will remain until they are at least 1.3M (4 feet) in length.
Then, the male sharks head north, while the females swim south.
As the blue shark has frequently been spotted in groups of all female or all male, similarly sized fish, this extraordinary grouping by sex would seem to stem from some instinct they are born with.
An odd but worth noting fact about blue sharks is that the male bites the female to initiate sex.
As a result, female blue sharks have evolved to have a thick skin so that she is not harmed by the male's bites.
The video above briefly mentions this thick skin as the tags they use on the sharks go under the skin, apparently without causing pain.
How to recognise a Blue Shark?
Blue sharks are long, slim, streamlined fish with rounded, elongated snouts and big eyes.
They are dark blue on top, light blue along the flank, and white underneath.
Probably their most distinguishing feature is their elongated pectoral fins – those are the ones at the sides.
Unless you are diving, or ship-wrecked in the middle of the ocean, you are unlikely to meet one.
There is some suggestion that blue sharks would eat you if you are injured and struggling in the ocean, but there is no proof of this.
You are more likely to get eaten by an oceanic whitetip shark, which you will instantly recognise from the white tips on its fins.
These are vicious predators which you wouldn’t wish on your worst enemy, but the blue shark is quite unlikely to take a bite unless you are dead or almost dead.
Should you ever be on vacation somewhere it is best to learn the name of the blue shark by its Latin name, Prionace glauca.
This is because other languages have different names for the blue shark, which in English is also known as blue dog and blue whaler, but in all languages it is called Prionace glauca.
It is estimated that 20 to 30 million blue sharks are killed every year by fishing.
While many of them are targeted for their fins, many more are caught in nets as an accidental by-catch.
Blue shark meat is not edible for long so their carcasses are mostly dumped.
It is only now that scientists are studying all sharks in detail, which should tell us more about these fascinating creatures.
The more we learn, the more we can find out how to save them from being fished out of existence.
Blue shark cartilage is often used in the alternative health market, promoting cancer-curing products that do not work.
sharkfacts (author) from UK on July 21, 2012:
@Marcy, thanks, maybe I will do that someday :)
@unknownspy, I think it's a shame to keep sharks in aquariums; in fact, they must be very unhappy which would make them more dangerous! They should be in the sea where they belong, and maybe we should stay out of the waters where they live. Blue sharks will not come near us anyway, even in the water.
Life Under Construction from Neverland on July 21, 2012:
Im scared of sharks.. We have an aquarium last time and my aunt bought 2 sharks..they're really scary. I loved reading your hub though..makes me aware of info and details about these creatures.
Marcy Goodfleisch from Planet Earth on July 21, 2012:
You could turn this and some of your other work into a book - excellent information and super interesting to read. I love the map, by the way!
sharkfacts (author) from UK on February 22, 2012:
Thanks jellygator. Blue sharks are amazing creatures.
jellygator from USA on February 21, 2012:
Voted up and beautiful.
sharkfacts (author) from UK on February 07, 2012:
You are right, I can see killing them if its you against them, but not for sport, and certainly not just for their fins.
CMHypno from Other Side of the Sun on February 07, 2012:
Interesting shark facts and you can't really blame them for attacking humans who are trying to kill them. Why is it that so many people seem to get pleasure from killing sharks and other large animals? If its for food that's different, but just to say you've done it or for a trophy is a bit sick.
sharkfacts (author) from UK on February 07, 2012:
Thanks, did you watch the videos? That was a brilliant piece of filming IMO. They put a shark cage out to protect the cameraman but he decided to leave the cage - just as well because a few minutes later a slim blue shark went in, straight through the bars, but couldn't get out again, till the diver helped it. If he had been in the cage at the time, it could bitten him as it would have felt trapped.
James Kenny from Birmingham, England on February 07, 2012:
A great, detailed article. Packed full of information on a magnificent Shark. Voted up.