Sharks - Why We Should Care About Them

Recently their has been a lot of hype about sharks and shark conservation with numerous online petitions circulating to ban shark finning and even stop shark fishing altogether. As scuba divers we love the underwater environment and all that lives below the surface, and it is up to us to help spread the word about this most delicate of eco systems and how fragile it is. Sharks are in desperate need of our help, over 100 million are killed each year, in the few decades shark populations have fallen by around 90% due to mankind. If we are going to save these beautiful creatures then we need to act now, but why are they so important? We take a closer look.

A whitetip reef shark resting on the ocean floor

Introduction

There are around 500 species of sharks and over 1200 species of cartilaginous fishes which includes sharks as well as rays and skates. Sharks come in all sorts of shapes and sizes from the tiny dwarf lantern shark which is about the size of a human hand and lives at depths of around 280 - 400m all the way to the largest of fish in the ocean, the majestic whale shark. In-between this there is so much variation, from the well known but miss understood great white shark, to the weird and wonderful wobbegong shark found in parts of southeast Asia, sharks live in all oceans and temperates of water. The Greenland shark is the longest lived of all vertebrate species with a lifespan between 300-500 years which is just mind blowing and live at depths of around 1500m, there are sharks that can walk out of water such as the leopard epaulette shark, but why am I telling you this? Its because sharks are endlessly fascinating, they aren’t the mindless killers that film and some media reports would have you believe. They play an important part in the delicate eco systems beneath the surface and a world without them would be very different indeed.

Whitetip reef shark

Sharks have been around for 450million years, that’s before the dinosaurs arrived and have survived 5 mass extinction events however their future is now balanced on a knife edge thanks to the invention of the most sophisticated killer the world has known - humans.

Importance to Eco-Systems

Sharks play an incredibly important role in helping to maintain healthy eco-systems and maintain the balance that is so important. There are numerous example fo where this happens, for example on coral reefs sharks keep the populations of carnivorous fish in check, which in turn allows the herbivorous fish to thrive, why is this important? Well the herbivorous fish graze on micro algae and this allows corals to grow and flourish. Without this regulation the corals would be overgrown by algae and die off.

A blacktip reef shark and whitetip reef shark

In the north Atlantic ocean the loss of the 11 great sharks, sharks more than two meters on length, has had unforeseen consequences. All of these 11 species of great shark have declined by more than 50% in the last 15 years which has led to their traditional prey, rays & skates to increase by as much as 10 fold. The effect of this increase of population of rays has led to the collapse of scallop fisheries. The species that benefitted the decrease of great sharks the most was the cownose ray which eats scallops, calms and oysters, without the sharks to keep their numbers in check the rays have eaten all of the scallops and are expected to continue eating their way through the clams and oysters, while the loss of a seafood may sound trivial on the face of it the consequences could be far more serious - scallops, clams and oysters are bivalves which act as a filtration system for the ocean, without them coastal areas could experience uncontrolled algal blooms which would damage an already stressed eco-system further. This is another demonstration of the effect the loss of sharks can have on a eco system.

Sharks are also the doctors of the ocean too, they keep the populations that they prey on genetically healthy too by removing disease and sickness from the gene pool - they prey on the weaker individuals and this ensures that any weak or mutated genes do not get passed on, survival of the fittest and an example of natural selection in action.

Inspiration for Innovative Design

Sharks are also, believe it or not, the inspiration for some of the most innovative designs. Sharks are able to swim at great speed due to small scales on their skin called denticles - these denticles help to reduce drag and turbulence and increase efficiency as they swim through the water. This design has been mimicked by scientists and sportswear manufacturers to produce swimsuits to make swimmers sleaker in the water and reduce resistance! One renewable energy company has even copied a sharks tail to capture the energy from waves and convert it into renewable energy in the form of electricity.

Shark Finning & Longlines

Shark finning is a controversial practise that takes place world wide to feed demand for shark fin soup, a delicacy in many parts of Asia and a display of social status due to its cost. Shark finning is a brutal practise where sharks are caught, their fins removed and then thrown back into the ocean as the rest of their body is bulky, takes up room and therefore reduces profitability. The issue is that, without their fins sharks can’t swim and sink to the bottom of the ocean where they drown or are eaten by other predators - think of how you would feel sinking to the bottom of the sea without being able to do anything about it. Its such a brutal practise and needs to stop. The other threat to sharks is a fishing method known as long lining - as fish populations decrease globally due to over fishing nets get larger & longer. Many sharks get caught up in these nets and are discarded as they are not the primary target. This fishing practise is also decimating shark populations globally.

A Ray of Hope

It’s not all doom and gloom however, there is a ray of hope. Places such as the Bahamas, South Africa, the Galapagos Islands and Palau have shown their is an alternative. Palau in particular has had great success in protecting sharks, declaring themselves as a shark sanctuary back in 2009 by banning all commercial fishing across an area of 600,000 sq km of ocean - about the size of France. By creating this so called shark sanctuary there have not only been numerous ecological benefits but a surge in tourism too. Divers from around the world flock to Palau for the amazing scuba diving on offer at sites such as the Blue Corner and German Channel. It has been estimated that in Palau a single reef shark can bring in around $2.4m to the economy over a ten year period, compared to just being worth $100 dead. This shows its not just about conservation, conservation makes good business sense too! In Australia shark tourism is worth around $18m dollars annually to the regional economy, other studies in the Bahamas show a single reef shark is worth $250,000 as a result of dive tourism vs a one time catch value of $50, in Belize a whale shark can bring in as much as $2m dollars over the course of its lifetime. Surely its time that we start looking past the short term benefits of sharks and look to the longer term, healthier reefs, healthier oceans and a healthier planet. As Dr Sylvie Earle once said, no blue, no green - the oceans are essential to the well being of our planet and sharks are essential to the well being of the ocean.

Whale sharks are the largest fish in the ocean