If you’re on a boat and sharks start exploding out of the water around you, each one twisting through the air like it swallowed a fidget spinner, you might be surrounded by spinner sharks.
When these predators come across a school of baitfish, they whirl through the water, spinning on their axis and snapping their jaws to try to catch a bite. Sometimes they get up such momentum while launching themselves towards the fishes that they fully leave the water, spinning two or three times in the air before splashing back down again.
What are spinner sharks?
This species is a type of requiem shark (related to blue, bull and tiger sharks). Their classic ‘sharky’ look, slender body and iconic black tipped fins mean they are often confused with blacktip sharks.
These animals are known – as their name suggests – for their iconic spinning behaviour, a key tactic they use to catch fish while hunting. They can be found in large aggregations and put on an extraordinary display when several sharks are all breaching together.
What do spinner sharks look like?
With their long, slender body and pointed snout, spinner sharks look similar to blacktips (hence why they are sometimes called great blacktip sharks) and the two are often confused for each other.
In adult sharks, the easiest way to tell the difference is to look at their anal fin. If it has a black tip, you’re looking at a spinner shark. If it doesn’t, it’s a black tip. Somewhat confusingly, this trick doesn’t work for young spinner sharks as the species is born without these marking and develops them as they grow older.
Spinner sharks also grow larger than blacktips and their first dorsal fin is located further behind their pectoral fin.
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How big are spinner sharks?
They are around 195cm long on average but can sometimes reach around 300cm and weigh around 56kg
Where do spinner sharks live?
These migratory sharks are found in the Mediterranean Sea, the Atlantic Ocean and the Indo-West Pacific Oceans. They like to spend time in shallow, nearshore waters but can swim as deep as 100 metres and are also found offshore.
What do they eat?
They mainly eat small bony fishes, including anchovies, bonito, herring, jacks, mullets, sardines and tuna. They will sometimes also eat stingrays, squid, cuttlefish and octopuses.
Because their diet is largely made up of fishes, they have a narrow jaw and small, narrow cusped teeth which are designed to pierce and grip onto slippery fish.
How do they hunt?
Spinner sharks get their name from their unique hunting strategy. The charge upwards through schools of fish, twirling as they go and sometimes even breaking the surface of the water, leaping into the air (still spinning) then flopping back into the water.
Spinning around their axis in this way could help the sharks improve their chances of catching a fish because they can snap at the school from every angle.
Sometimes large feeding aggregations of spinner sharks all gather in the same area – it’s quite a sight to see shark after shark launch themselves out of the water like a spinning top.
When the opportunity presents itself, these wily predators are also known to scavenge discarded catch dumped overboard by fishing vessels. A free feast!
How do they reproduce?
Mature female spinner sharks give live birth to a littler of between three and 15 pups every other year. Gestation takes around 12 to 15 months – during which time the embryos are sustained by the yolk sac – and the babies are fully independent from the moment they’re born.
The adults don’t provide any parental care but females give birth in shallow coastal waters where the little ones are at a lower risk from predators.
Are they dangerous to humans?
No. Many people think all sharks are scary and pose a threat to humans but this just isn’t true. Globally each year, there are fewer than 10 fatalities from unprovoked bites from all species of shark.
Spinner sharks have small, narrow teeth; perfect for snacking on fish and not designed to take down marine mammals. Humans certainly aren’t on their menu.
There have been some incidents, however. According to the International Shark Attack File’s data, there have been 16 unprovoked bites from spinner sharks. None were fatal.
Are they under threat?
The IUCN Red List of Threatened Species lists spinner sharks as vulnerable to extinction because populations are decreasing.
These majestic sharks are caught by fisheries around the world – both on purpose and accidentally – and can also be killed by shark nets. Its hard to know exactly how many die in fisheries because they’re often confused with blacktip sharks.
When they’re caught on a hook, this species uses its iconic spin to try to get free: leaping out of the water and spinning in circles.
