About the event
Our Events Developer Lauren explains why we need to rethink the reputation of sharks.
If you’ve seen Jaws and you’re a reasonable person, you should be able to see that the bad guy of the film is not, in fact, the shark. The real bad guy was the mayor.
Since the 1970s shark populations have declined and some researchers think that this is in part due to the vengeful and calculating characterisation of the Great White in the blockbuster film.
Although not an irrational fear (have you seen those teeth?) the scale of public fear of sharks and the responses to sharks being spotted along coasts are vastly out of proportion.
In parts of western Australia in 2014, traps were set up to indiscriminately catch and kill sharks that dared venture too close to human swimming areas. The setting of traps was stopped less than a year later, but the message sent to the public was clear, all sharks in the area were a threat to humans.
Despite their bad rep, sharks actually very rarely eat, or even attack humans. Shark species mostly feed on small fish and small ocean invertebrates such as crabs, with some larger species hunting seals and other marine mammals.
Worldwide, the species that killed the most humans (72,500x more than sharks in 2014!) was..... Mosquitos. And in a not too far off second...other humans.
Sharks are continually killed by humans, on purpose and often illegally, for meat or use in traditional medicine for their fins, organs, and skin, or by accident as by-catch in fishing nets.
Dried shark fins for sale in a market in Ecuador © Alex Gabb
Lots of different sharks are hunted for their liver oil, squalene, for use in skincare products. However, lots of the sharks caught for this purpose don’t actually even make squalene, only those in the family Squalidea (Dogfish) produce it.
Spiny Dogfish, Squalus acanthias. By Doug Costa, NOAA/SBNMS
The IUCN (the folks that tell us which animal species are endangered) have recently said that “a quarter of sharks and rays are threatened with extinction”.
The amount of sharks killed each year (around 97 million sharks in 2010) is entirely unsustainable and if left to continue, could lead to the extinction of up to 250 species of sharks and rays. Peter Benchley, the creator of Jaws, was deeply regretful of his role in the decline of sharks, becoming an advocate for marine conservation later in his life.
So in summary: Sharks – NOT THE BAD GUYS. They rarely attack people and are unfairly persecuted.
On to the fun bit, some of the coolest adaptations of sharks, and a couple of my favourite species in a bit more detail.
Electrosensors – Lorenzini ampoules
Every living thing emits a small but detectable electric field; movement of muscles, heart beats, and brain activity all produce an electric field. Sharks and rays have a specialised organ, just like the eye or ear, which is able to detect these electric fields and tell the shark where prey might be hiding.
Pores containing the Ampullae of Lorenzini , by Albert kok - Own work, CC BY-SA 3.0
Being that sharks are fish, they are covered in scales. Shark scales are called placoid scales or dermal denticles (denticle meaning ‘small tooth’). They have the same kind of structure as human teeth, with the hard outer layer of enamel-like material, a centre filled with blood vessels and nerves, and a mid-layer of dentine. These scales are shaped in a way that reduces water resistance (drag) on the surface of the shark, helping it to swim better through the water, and they reduce the turbulence of the water as the shark glides through it, making it much quieter compared to other fish! The shape of the scales also helps them to stay clean through something called the lotus effect.
Shark skin placoid scales through an electron microscope, by Pascal Deynat/Odontobase - Own work, CC BY-SA 3.0
I think sharks are incredibly cool and I definitely have favourites, but to talk with a bit more authority, I’ve asked guest writer, research assistant, shark lover (and my pal) Alex Gabb to explain why she thinks her top 3 species deserve your respect and adoration.
Whale shark (Rhincodon Typus)
Whale sharks are the largest, non-mammal vertebrate and the largest fish in the sea. The largest individual ever reported was almost 20m in length! They have dark blue skin marked with white stripes and dots that are actually unique to each shark, a bit like a finger print. Scientists using growth rings on vertebrae estimate that these amazing animals could live up to 130 years old! Whale sharks have large mouths filled with 300 tiny teeth and filter pads that they use to filter feed on plankton. The whale shark shares this method of feeding with its two distant cousins, the megamouth shark and the basking shark. Take a look at the family photos and I think you’ll agree that whale sharks lucked out in the looks department! These stunning animals live largely solitary lives but are known to congregate at large feeding events at the same coastal sites every year.
Scalloped Hammerhead Shark (Sphyrna Lewini)
Scalloped hammerheads get their name from their notched or “scalloped”, hammer-shaped heads. During the daytime, they “school” together in large groups that can reach up to 500 individuals! Scalloped hammerheads are the only shark to practice schooling and while it is a spectacular site, it is quite a puzzling behaviour. Small fish generally gather to help limit threats from predators but due to their position at the top of the food chain this problem doesn’t really apply to sharks. Other animals gather in groups to try and hunt down larger prey, but sharks are solitary hunters, so this doesn’t explain it either. Biologists believe this behaviour is in fact something called refuging where individuals group in a safe space near their food source while they wait to go off in their separate directions to hunt. I like to think that maybe they just like the company! Sharks have much more complex social lives then we’ve been led to believe.
Bigeye Thresher Shark (Alopias Superciliosus)
Pelagic thresher (Alopias pelagicus) is a close relative of the Bigeye thresher. Look how long its tail is! By Thomas Alexander - Own work, CC BY-SA 4.0
Bigeye threshers have, you guessed it, very big eyes! These eyes make them well adapted for hunting in low light conditions and have the unintended side-effect of making these sharks look incredibly cute. Thresher sharks belong to the Alopiidae family and are best recognised for their enormous tail fins. The bigeye thresher has the longest tail of all 3 thresher species with the upper lobe of the big-eyed thresher’s fin making up nearly half of the animal’s total length. They use these tails to whip and stun their prey, which is a truly remarkable behaviour and is well worth a watch on YouTube – think India Jones-style. Females usually only give birth to two pups at a time making these spectacular animals particularly vulnerable to threats like overfishing.
Hopefully you’ve been inspired to learn more these incredible sharks, and if you didn’t already, come to understand that sharks are not the bad guys in Jaws or real life!