World Without Sharks
They have patrolled our oceans for more than 400 million years, but, for the sake of a bowl of soup, the very existence of sharks is now under threat
Would you want to live in a world without sharks?
Before emotion charges you with a knee-jerk response, it is essential to understand what sharks are, away from the hyperbole and misconceptions, and to understand what exactly is their role in the ocean ecosystem. What we talk about when we talk about sharks is many things, often conflicting: some scientific, some fanciful, and some absolute.
Without question, the term ‘sharks’ has become humankind’s shorthand for ‘the underwater bogeyman’. Sharks have been vilified and set upon the consciousness of mankind as ‘the ultimate embodiment of evil in the sea’.
There is nothing so unsettling in the human thought process than anything to do with the idea of being devoured. It creates a lurid fascination and leaves little to the imagination.
The derivation of the word ‘shark’ itself is clouded in uncertainty, but what we can be sure of is its meaning today. The word ‘shark’ describes members of superorder Selachimorpha, a specific branch of the elasmobranchii, a class that also includes skates and rays.
For animals that evoke so much fear in humans, so much remains unknown about them, including a consensus as to how many different species exist. Estimates of their individual species range wildly, from 370 to 460 species of sharks, distributed worldwide, falling into eight orders encompassing remarkable diversity. They have a presence in every ocean, with species inhabiting waters from just below the surface to as deep as 1,500m. Shark species run the full gamut in size from the largest fish in the ocean, the 12m-plus whale shark, to the dwarf lantern shark, which matures at just under 22cm in length.
There is tremendous variation among the large and diverse group of species placed under the umbrella term ‘sharks.’ Some species have a sedentary life and move in a limited area, while others cover hundreds of kilometres in a year. All in all, there is a shark for every occasion.
And although there is no such thing as a typical shark, there is a certain shark body form from which the majority of sharks share a degree of commonality: a streamlined body covered in placoid scales called denticles; a flexible jaw filled with teeth; a rigid, prominent first dorsal fin; five to seven gill slits; and a heterocercal or homocercal tail. The entire family of Carcharhinidae, the Requiem sharks, and members of the Lamnidae, makos and the infamous great white shark, pretty much fit this general description of sharks. It is sharks from these families that most people think of when they hear the word ‘shark’.
Decades of scientific research suggest sharks are intelligent animals, with a brain to body mass ratio similar to some mammals, and many species display social complexity. They have a highly developed sense of smell; exceptional eyesight; excellent hearing; a lateral line to identify the environment around them in a detailed representation; and 0 millionan electroreceptive sense that perceives the electric fields and impulses given off by living organisms. With this suite of senses, sharks are unsurpassed as predators.
All sharks are predators, be they plankton-feeding sharks of the deep sea or the marine-mammal-eating great whites, but few sharks are apex predators – or, to be accurate, apex predators all the time. For example, a reef shark can be a top level predator and would be an apex predator were it not for co-inhabiting the environment with a tiger shark, which has no qualms about eating a smaller reef shark relative.
The conventional wisdom taught at schools not so long ago was that all living creatures in each ecosystem are represented somewhere along a food chain: a more or less linear arrangement, with predators at the top, feeding upon consumers in the middle, with a resource at the bottom.
Alas, the real-life mechanics of nature are both subtler and more complex than that. In nature, the more biodiverse an environment, the more multiple connections between various trophic level animals than a simple linear flow and more consequences for the ecosystem as a whole by altering (eliminating) the various trophic players.
Predators eat more than one type of prey, which keeps the ecosystem in balance, as the loss of a single type of prey does not destabilise the system. The greater the biodiversity, the more connections and more interdependencies between organisms comprising it.
These multiple connections from the top downwards to the other levels are essential to maintain a steady state of equilibrium in a functioning, healthy, self-perpetuating ecosystem. Loss of equilibrium causes dramatic changes within the ecosystem, including, in worst-case scenarios, mass extinctions.
Studies close to Pacific coastal areas were the first step into analysis of the interconnectedness of food webs in the ocean. Sea otters were determined to play a keystone role in the kelp forest communities near shore. The sea otter’s diet of sea urchins kept the sea urchin populations in check. When sea otters were removed from the ecosystem, sea urchins proliferated and tended to overgraze the kelp and its holdfasts on the bottom, causing the elimination of kelp in certain areas. When sea otters were reintroduced and their numbers increased, balance in the system was regained and sea otter, kelp and sea urchins coexisted and interacted in a healthy, stable ecosystem.
In the Caribbean, many islands have allowed a localised extinction of their shark species and with time, this loss has manifest itself in the degradation of its coral reefs. Corals thrive only under certain conditions, one of which is being in relatively shallow water that receives ample sunlight, which is also the essential requirement for algae and plant-life, with which the coral competes for space, what you might call reef real estate. Herbivorous fish feed solely on this vegetarian richness and feed continuously, which has the effect of containing the fast-growing algae before it overgrows the living coral polyps. Removal of sharks as top-level predators has the carry-on effect that the sharks are not predating upon the jacks and snappers that feed upon the parrotfish and other herbivores. The herbivore population crashes with the over abundance of their predators and the algae and plants grow and flourish, unchecked, over the coral polyps, ultimately suffocating them.
Along the east coast of the United States, the decline of larger sharks is said to be the cause of increased numbers of cownosed rays, which in the past had been prey to larger shark species. The postulated increase in rays is said to be the reason why commercially valuable shellfish populations have crashed. It is hard to believe that there has been a population explosion of cownose rays (it takes them a long time to reach maturity), but it is possible that by removing the cownosed rays’ predators, more rays are making it to maturity and/or their populations have expanded into areas where they were not previously considered to be in substantial numbers.
In a healthy environment, as top-level predators, the majority of sharks are understood to be the stabilising influence in each ecosystem they dominate. They carry out this function by providing services essential to maintaining a balanced, healthy environment: they cull the unfit; they keep their neighbours on a high state of vigilance, in some instances creating a displacement effect that keeps animals sparse in areas where they would be vulnerable; they maintain the balance between differing species so no single population structure goes out of control; and some species assure prey populations are kept in prime condition by weeding out the unfit, so the strongest and healthiest are able to reproduce and pass along their superior genes.
So, the question remains: Would you want to live in a world without sharks?
As a diver, the answer would unequivocally be ‘no’. Over a lifetime of diving experiences, I can safely vouch that the word ‘shark’ is the one word uttered more than any other diving or ocean related word on any dive boat around the world. Without sharks, the ocean becomes less interesting and the diving becomes less interesting.
But beyond ‘selfish’ love of nature for its own sake, self-interested man surely must appreciate that without sharks, ecosystems collapse, collapse fully and completely and they do not rebound. Unlike terrestrial national parks, predator reintroductions are not possible with sharks. There is no successful captive breeding program. Once gone, they are gone for good. So what can be done to prevent a world without sharks?
Activism is the only solution. Get involved. Nature belongs to everyone. It can be exploited or protected. It is up to you.
The most devastating damage done to shark populations has occurred in the past two decades and goes on, non-stop. Virtually all shark species have become targeted to fuel the shark fin soup industry, due to the ever-increasing prosperity of China and the ascendancy of its suddenly affluent middle class. For the sake of a bowl of soup, tens of millions of sharks are caught annually, their fins cut off, sometimes while the animal is still alive and often the remainder of the shark’s finless carcass is discarded back into the ocean, of no further commercial value to the fishermen.
Tens upon tens of millions of sharks are killed, deliberately and with great effort, every year. There is no possibility that such unregulated harvests are sustainable.
The battle to save sharks must be fought through habitat protection, education, and legislation. Of these, shark sanctuaries, marine parks and reserves, such as Marine Protected Areas (MPAs) are the most vital. Shark species must have a designated refuge from fishermen; a place where they can live and thrive in a healthy ecosystem, reach sexual maturity and create new generations of offspring.
Education is an essential component in the battle to save sharks. Education is a matter of learning for oneself and imparting knowledge to others. There are many misconceptions about sharks, but these misconceptions and outright falsehoods can be rectified through education.
Slowly, the word is getting out that sharks are not man-eaters out to get bathers and divers, but an integral part of the ecosystem that belongs in the oceans more than people do. But for every positive influence that makes it into the public perception, there is always an erroneous negative piece of wildlife fiction posing as a documentary brought to a new and gullible audience. Further, it is astonishing how many people are unaware of the insidious practice of cutting the fins off living sharks and dumping them back into the sea to slowly suffocate, all for the bowl of reconstituted dried shark’s fin sitting in a broth of chicken and pork stock. Learn about shark fin soup, why it is not a cultural necessity to Asian cultures and spread the word to others. For example, when confronted with shark fin soup on the menu of a Chinese restaurant, one can take the opportunity to educate the proprietor of the restaurant why shark fin soup should never be served.
The third area where a difference can be made is through legislation. Everyone who has a vote has a say in their future. Every country has lawmakers who are ostensibly beholden to their constituency. There are many laws before legislative bodies seeking shark sanctuaries and/or outlawing the sale of shark products. Make your voice heard with your representative.
Every shark saved helps tip the balance back towards equilibrium, however slightly. No one wants attend a memorial service in the near future for a great family of animals needlessly extirpated. No one with a brain or a heart would want to live in a world without sharks.