Up Close and Personal With… Sharks

Sharks are quite possibly one of the most misunderstood creatures of the ocean yet they actually have a very essential role in keeping our waters in check and despite what many may say, they deserve as much protection from human perils as other ocean goers. The likes of the Great White have given sharks their menacing reputation, however there are over 500 species of shark with each one being unique in their own way. These famous fish vary in size with the Dwarf Lantern Shark being only the size of a human hand whilst friendly Whale Sharks can reach over 12 metres. Despite what rumours may say, sharks do not just linger in the deeper waters of our crowded surfing spots but actually live in a variety of habitats from coral reefs to the pitch black deep sea to the eerie Arctic Ocean. The Greenland Shark which glides under the sparkling sea ice is actually the longest living vertebrate on Earth, with some individuals reaching 400 years old!

So what makes these oversized fish so important to our oceans? Many sharks are apex predators which means they are at the top of the food chain in their ecosystem, safe from the hungry jaws of other creatures and able to take their pick of the many smaller prey species. Hungry sharks are essential for keeping all the other populations of fish in the right balance with each other. For example, if our reef sharks were lost, large fish such as Groupers would increase as they become free from the shackles of their main predator. In turn, the booming Grouper population would feast widely on small herbivorous fish which feed on marine plants. As the numbers of small plant-loving fish fall, macroalgae suddenly blooms, expands and eventually smothers our reefs, blocking essential sunlight from our bright corals which, over time, causes them to lose their iconic colours. Without top predators like sharks, our oceans would become an almost unrecognisable place as the delicate balance of different species would be shaken and redesigned. Sharks often take the lazy option and feed on the weak and sick individuals of a species, leaving only the fighting fit members of the population swimming free which helps strengthen the ecosystem and over time, means that the healthiest individuals pass on their genes to the next generation.

In order to keep up with all this ocean maintenance, sharks have several rows of teeth which they can lose and replace thousands of times within their lives. In fact, a Sandbar Shark will often have 35,000 pointy pearly whites over their roughly 15 year lifespan. More helpful, however, in their search for food is their sneaky sixth sense. Sharks have small pores found on their noses which can sense the electrical field which surrounds all of us. When underwater animals make any muscular movement, such as the waggle of a tail or the flick of their head, they create a tiny electrical current which very slightly changes the voltage of the surrounding electrical field. Sharks’ snouts can sense the tiniest change in voltage and send a signal to their brains telling them something is living nearby. In Great White Sharks, once they are in the last few feet of their attack, their eyes roll into the back of their head to protect themselves and this electroreception completely takes over as they latch onto their unsuspecting prey. This sixth sense also allows them to feel the magnetic field which cloaks Earth which scientists think may help sharks navigate during migration. The force of this field is roughly the equivalent of 0.25% of the force a fridge magnet gives out which gives you an idea of how powerful this talent is!

Despite what famous films, snappy headlines and story books tell us, sharks really are just not that interested in us humans. As you can see from just these few insights into their lives, they are, in reality, a complicated and fascinating bunch of creatures. Whilst many of us have a fear of sharks, there is only a one in a 11,5000,000 chance of being bitten by one of these predators whilst the risk of dying is even lower. Driving a car, being struck by lightning or being attacked by a dog are all significantly more likely but sharks still lack the protection they deserve due to our pretty irrational fears. Did you know that only 6% of shark species have been known to attack humans whilst most prefer to snack on molluscs, small fish, krill or maybe the odd seal? Whilst Whale Sharks and Basking Sharks do have teeth, they do not even use them to eat! So what are the threats facing these misunderstood fish?

Sharks have glided around the Earth for over 400 million years; that is significantly longer than the time dinosaurs spent lumbering across the soil, yet our modern day fishing practices are one of the largest threats facing these ancient critters. It is estimated that 100 million sharks are killed every year, most of which are used to satisfy the large Asian demand for expensive shark fin soup. Many of the sharks caught by fishermen have their fins removed and then wastefully, the rest of the shark is dumped back into the sea half alive to suffer a slow death. Other fishermen take the entire shark back to land where they are used for leather goods, tooth jewellery, traditional medicine or as cosmetics. It might surprise you but shark liver oil is actually easily available online in the form of supplements, lipsticks, moisturisers or sun cream despite a high number of sustainable alternatives. With sharks in high demand for many products, they are being plucked from the sea faster than they can reproduce which is leading to dwindling populations of these important ocean creatures. In many countries, shark fishing is illegal but with the ocean being such a vast and isolated expanse, it is hard for patrollers to stop all illegal activity. To help, you can support or petition for new laws and practices which aim to stop illegal fishing once and for all and ensure you avoid any products which contain shark to stop fuelling the unsustainable fishing industries. Alongside dolphins, seabirds and turtles, sharks are also a victim of bycatch as invisible fishing lines and baited hooks are one enemy these great predators are unable to escape. In particular, tuna fisheries often pull up a large number of sharks alongside their target catch so next time you are at the supermarket, make sure the seafood you are buying comes from sustainable sources using sustainable fishing methods.

The loss of some of our beautiful underwater environments is also proving a large problem for our sharks. As mangroves are chopped down either for wood or as space for developments, young sharks lose their safe hiding places where they were free to grow into successful hunters away from the hungry eyes of larger animals. As our coral reefs vanish due to destructive fishing, climate change and chemical run-off into the ocean, sharks lose their essential hunting and mating grounds which help sustain their population numbers.

Climate change in particular is severely affecting shark populations around the world for several reasons. Firstly, many species of shark have extremely long pregnancies with the Greeneye Dogfish spending 31 months growing their young. In addition to this, many sharks have long life spans which means it takes them many years to reach sexual maturity and start producing young. Even when they do give birth, some sharks only give birth to two tiny tots whilst others give birth to over 100. This means that population growth amongst some sharks is often very slow, a disaster in the face of climate change. With so many years between each new generation, it means that certain shark species will take a very long time to adapt to warmer waters which reduces their ability to survive new ocean conditions. Whilst species such as the Epaulette Shark already seem well adapted to climate change as they survive in Australia’s hot tidal waters and can go without oxygen for 90 minutes, others like the Ghostshark can become quickly threatened if their small home turf suddenly warms.

Whilst Great Whites were thought to be the oceans greatest villain in the 1970s as Jaws hit cinema screens, today in the 21st century we have realised that actually manmade plastic is the greatest truant. Even these epic hunters cannot escape the wrath of plastic as they become entangled and impaled. Plastic is a particularly large problem for Whale Sharks which filter feed in the highly polluted waters of Indonesia. With each big gulp of water, they expel excess seawater and swallow the tiny fish and now also tiny microplastics which hide within them, often later leading to disease due to the chemicals wrapped around our waste.

To help our sharks, there are many things you can do, whether that be choosing sustainable seafood, supporting a shark conservation charity, ditching plastic for good or doing your bit to reduce climate change. Maybe the best thing you can do for sharks is to educate your friends and family of their importance by sharing shark facts and stories on social media to help end their stigmatised image which stops so many people from helping these majestic creatures. Whatever you choose to do, you are not alone. Scientists are tagging and tracking shark species around the world to better understand their behaviour and allow us to create safe protected areas in the regions where hundreds of sharks congregate. Other organisations such as the WWF are pushing for shark species to be listed on international treaties as endangered animals which cannot be exported across borders to help stop the illegal trade in shark goods. Let’s hope that the great work continues and that one day, sharks will overcome all the human challenges facing them to become the ocean’s top triumphs once more.

By Neve McCracken-Heywood