Sharks and Extinction: The Uncertain Future of an Ancient Lineage
More than 400 million years ago, the first sharks ventured through the dangerous seas of the Silurian age. Diminutive and seemingly insignificant, these fragile new species would pave the road for an astounding lineage, one that would eventually dominate the seas and supplant the fearsome predators that could not demonstrate the same great resilience in the face of nature’s greatest challenges. Mass extinctions would eventually take the dinosaurs and many other ruling animals, whether of the land, sea, or air, but the sharks always remained. Ages came and went, but these mysterious and formidable survivors continued onwards, adapting to new ecological changes and maintaining a dominant hold on the marine world. With the passing time came many different forms of sharks, some of these familiar to us, while others nothing short of strange and alien. To this day, sharks continue to grace the oceans with their presence, a testament to the adaptive potential that carried this ancient lineage through the rough and dangerous roads of natural history. Today’s sharks continue to amaze us with their variety and behavior; mighty great white sharks leap out of the water as they clamp their jaws around their seal prey, giant whale sharks slowly drift through the open ocean as they search for and feed on microscopic plankton, secretive six-gilled sharks travel in the deep, frigid depths of the ocean floor, and exotic hammerhead sharks gather in great numbers mid-summer as they migrate towards cooler waters. These are just some examples of the many fascinating observations made in the world of sharks. However, despite their great history and power to survive, the future of many sharks is now threatened like never before; the greatest predators of the sea are being selectively destroyed in massive numbers by a relatively new and dangerous competitor: man. The history between these two great survivors is not particularly long, but undoubtedly intense. Ever since humans first explored the marine world, they encountered dangerous new hurdles beyond their expectations, among them sharks. As man became more dependent on the ocean for food and also recreation, sharks and people began to cross paths repeatedly, sometimes with grim outcomes. In time, the relationship between man and sharks worsened, and many would develop an irrational fear, and even hatred, of sharks. Humans would eventually begin hunting more and more sharks, sometimes out of spite or for revenge after the death of a person in a rare shark attack. Man would also look to sharks as a food source, and eventually would begin pressuring shark populations with excessive hunting. Humans would also begin to indirectly threaten sharks via habitat destruction and pollution, further damaging shark populations. Needless to say, it is easy to see that sharks have become the far greater victim in this tense relationship. However, were sharks such problematic creatures to begin with? As it turns out, sharks are severely misunderstood animals. In reality, most sharks are indifferent to humans and pose no threat. Researchers can also understand the reasons for the behavior of those few species which can be dangerous to humans, and it is clear that in order to coexist with these animals, people must strive to understand why sharks behave the way they do. With the proper understanding comes a far better future for both man and sharks, and perhaps the replacement of fear for these animals with fascination. Unfortunately, while more and more people have become aware of the undeserved notoriety sharks have been branded with, the excessive destruction of these animals at the hands of man continues to take place on a daily basis. These beautiful animals, members of an ancient lineage far preceding man, are now being pushed to the edge of extinction as their unnecessary slaughter continues. To see these magnificent animals destroyed for such unjustifiable reasons would be nothing short of tragic. And yet, there may be more than simply moral reasons for the protection of these animals. With their longstanding roles as important members of the marine ecosystem, the destruction of sharks would lead to severe problems for the marine food chain. Sharks help maintain the health of ecosystems, which would become unbalanced with the depletion of these vital predators. Eventually, the outcomes of these events would even hurt us! It is important to understand how sharks are being threatened, and what can be done to save these incredible animals. Furthermore, one should strive to understand how sharks interact with their environment, how they maintain the health of ecosystems, and just how the future of the marine food chain would be crippled without their influence. Sharks have come too far just to be destroyed for such unacceptable reasons. Their extinction would produce nothing but disaster for the marine world, a future that must be avoided at all costs.
The shark has long been the media’s favored “monster.” Shark attacks and sightings attract the attention of television news shows, magazines, and newspapers every single year, as this produces ratings and sells more magazines for their companies. From a business perspective, it makes perfect sense. After all, what better to grab the attention of the masses than a story about yet another “man-eating” shark? Shark attacks were a particularly strong focus during 2001, when a violent encounter with a bull shark resulted in a young child losing his arm while playing in the waters off Pensacola, Florida. Following this unfortunate event, any encounter with a shark, including insignificant ones, actually made prime time news. Time Magazine referred to 2001 as “The Summer of the Shark.” In reality, however, shark attacks have always been relatively infrequent events. Virtually any other kind of accident will often result in more human injury or death. To get a good idea of this, consider the fact that, on average, more people are killed by dogs or lightning strikes than by sharks. In fact, children are more likely to be killed while playing in a beach sand hole (due to it collapsing) than by a shark. However, the reality of the situation means little in the face of business or people’s morbid sense of thrill, and as a result, sharks will always attract an unnecessary amount of media attention.
In truth, sharks are the ones in trouble. While very few people are killed each year by sharks, up to 73 million sharks are killed every year by man. According to global reports, shark populations have declined by as much as 70-80%, and scientists estimate that 30% of all shark species are either threatened or near-threatened with extinction, with insufficient data for an additional 47% of species making it difficult to produce accurate assessments. While this would be a severe problem for any group of animals, it is especially harmful to shark populations because sharks grow slowly, mature fairly late into their lives, and produce few young throughout their life-spans.
Sharks are hunted for a wide variety of reasons, such as for food, their skin, and liver oil. One particular delicacy is shark fin soup, a popular dish in China and areas with large Chinese populations. It has been considered a savory dish since the Ming Dynasty, when only the Emperor and his guests ate it. Until about two decades ago, the dish was served mostly in areas such as Hong Kong and other cities with Chinese populations, yet scarcely in China itself. During this time, the relatively low consumption did not result in any real threat for sharks. However, with China’s population of 1.3 billion people now enjoying more prosperity, the dish has become much more popular. It is now commonly served at banquets, business dinners, and weddings. This greater demand for the soup has resulted in more sharks being hunted for their fins. The fins are much more valuable than the sharks’ meat (which is worth less than that of most fish), and averages out at US$540 (HK$3500) per pound. The impact of the rising demand for shark fin soup has resulted in greater hunting pressure on sharks, but its current day impact on shark populations is unclear, adding a discomforting level of uncertainty to an already alarming situation. It is known, however, that around 100 shark species are targeted by the fishing industry, with most of the catches being purely for their fins. This activity is extremely wasteful as well as abusive, as the fishermen cut off the animals’ fins while they are still alive and then throw them back into the water, where the shark either drowns (since most sharks need to move in order to pass water through their gills) or simply bleeds to death. The fins are then dried, stacked, and sold (often illegally). The buyers then extract the fins’ collagen fibers, clean them, and process them into the shark fin soup. The ridiculous nature of this entire situation is the end result that is the soup itself; not only is shark fin soup flavorless, it possesses absolutely no nutritional value, making it a dish served mainly for prestige purposes. Nonetheless, with the rising demand comes the excessive and unnecessary killing of sharks, and the shark populations plummet as a result. The oceans are being scoured clean of sharks, and poachers are even invading national marine parks like the Galapagos Islands in Ecuador and Cocos Island in Costa Rica to search for sharks.
Sharks which are used for more than their fins can become a source of meat. While nowhere as popular as shark fin soup, shark meat has nonetheless become a more common food item in recent years, and it is now possible to buy it in supermarkets in Europe, South America, and the USA. The species which is considered to provide the best shark meat of all is the shortfin mako, which is classified as being lower risk. However, more vulnerable species are also hunted for their meat, such as the porbeagle shark. The reason for the rising popularity of shark meat may be due to the declining numbers of many other fish species and people being encouraged to eat fish as a healthy alternative to meat. However, the Foods Standards Agency has advised against feeding children shark meat because of the high levels of methylmercury, which can cause damage to the nervous system.
Shark skins can be tanned and used as an alternative for leather products such as belts, boots, or bags. Shark liver oil contains squalene, which is extracted and used as a lubricant and in cosmetic and pharmaceutical products. The oil is also promoted as a complementary or alternative form of treatment for cancer and other diseases. Chemicals within it which are being studied for their potential anti-cancer properties include the previously mentioned squalene, as well as squalamine and alkylglycerols. However, current evidence does not support the idea that shark liver oil supplements function effectively against cancer in humans.
Sharks are sometimes also killed for their cartilage, which is thought to inhibit the growth of tumors. This is yet another belief which has very little scientific support. Furthermore, it originates in another popular false belief, the claim that sharks do not get cancer. The shark cartilage run was started by agro-biochemist Dr. William I. Lane in the pseudoscientific book “Sharks Don’t Get Cancer.” Its contents are based on a 1983 study by researchers from the Massachusetts Institute of Technology (MIT) in which they claimed that cartilage from calves and sharks could influence the blood supply and therefore, indirectly, the growth of tumors as well. The book cites questionable studies and presents shark cartilage as a universal remedy against cancer. William Lane, who by profession and as President of the American Fish Meal Trade Association was looking into investment possibilities in the fishing industry of Guinea on behalf of the Reagan administration in office at the time. The new proposed anti-cancer substance promised to create a billion dollar business, even for the clever William Lane himself, who owned one of the largest companies dealing with shark products. Smart business, perhaps, but nonetheless based on lies. Firstly, sharks can, in fact, get cancer, and there are currently 42 recognized cancer varieties in sharks and related species. Furthermore, there are, to this day, no serious scientific studies available in which treatment with shark cartilage has proven to have any effect on human cancer cells. At best, there are several not yet precisely defined active substances in cartilage (shark cartilage included) which have shown to inhibit the growth of certain tumors in the test tube. This does not, however, translate to shark cartilage being confirmed as an anti-cancer remedy by any means. The lack of good evidence eventually caught up with Dr. William Lane, when in June 30, 2002, the American Federal Trade Commission (FTC) ordered Lane Labs-USA Inc. and Cartilage Consultants to immediately stop marketing shark cartilage as a presumable remedy against cancer. Andrew Lane, the President of Lane Labs, and his already well known father Dr. William I. Lane, the owner of Cartilage Consultants, were accused of misleading advertising and marketing campaigns for their shark cartilage preparation “Benefin” and the sun cream “SkinAnswer” by acclaiming them as being effective against cancer. Furthermore, Lane Labs also received and paid a penalty $1 million because of unfair competition. There are those who still believe shark cartilage to be effective against cancer, and this unfortunately results in the wasting of more life as sharks are caught and killed due to this false claim.
The damage dealt to shark populations is not always intentional, however. A considerable number of sharks are killed as bycatch, animals killed accidentally while fishing for other targeted species. It is not only sharks and other untargeted fish which are lost as bycatch, but also marine birds, whales, dolphins and sea turtles. These animals are often discarded back into the sea and rarely appear in records, even where bycatch must be recorded. According to the Food and Agricultural Organization (FAO), there are few fisheries which do not result in bycatch of sharks and other animals, and an estimated 50% of the world catch of sharks is believed to be taken as bycatch, though there are lower estimates as well. Based on a much debated average weight of 15kg per shark across the species range, this could mean that a bycatch of about 26 million sharks goes unrecorded each year. Whenever the shark bycatches are recorded, the numbers are terribly high, sometimes actually exceeding the targeted catch. In the past, these sharks would have been thrown back into the ocean, or the lines cut. However, with the rising demand for shark fins, these bycatch sharks are now usually finned. While there are bycatch reduction methods available to fishermen, these may be rejected by those willing to profit from shark fins. The fishing gear used by fisheries has plays a part in the rate of shark bycatch. Easily the most indiscriminate gear is towed (trawl and seine) nets. Bottom trawl fisheries in coastal areas are thought to result in the largest bycatch of sharks as well as rays, although tuna purse seine nets and gillnets are occasionally responsible for large scale shark bycatch as well. Yet longlines are probably the most threatening fishing method with respect to shark bycatch. When one considers their widespread use as well as the great length of these lines and the number of hooks, it is not surprising that more sharks are caught as bycatch in longline fisheries than in any other fisheries on the high seas.
Habitat loss and pollution are other threats that must not be ignored. Coastal development has increased tremendously within the past century, and this has led to altered habitats and increased levels of pollution, which have resulted in the general environmental degradation observed in many areas. This can easily lead to problems for sharks, since many species use inshore coastal and estuarine habitats as safe areas for finding prey, giving birth, and growing up without the threat of the predators and competitors that they would have to contend with in deeper waters. As an example of the negative effect that coastal environmental changes can have on sharks, dredging in the Bahamas resulted in a 25% decline in juvenile lemon shark survival in recent years. Also, juvenile bull sharks have been trapped in the warm water outfalls in power plants in Florida. This entrapment keeps the sharks from taking part in seasonal migrations, and if the water from the power plant does not flow, the shark may succumb to thermal shock or thermal stress. This may also cause the sharks to cease seasonal migrations altogether. Sharks are just as susceptible to pollution and contamination of their habitats. Pollution in the ocean has either filtered from activities on land or been deposited directly into the water. Being apex predators with slow growth, sharks gradually accumulate the pollutants and toxins of their environment, including the toxins in their prey. Chemical pollution in the form of mercury, DDT, organochlorines, and other substances has been recorded in several shark populations near areas of human populations. Bull sharks in Florida have also been found to possess high levels of pharmaceuticals that are disposed of through waste water discharge. Put simply, sharks are heavily affected by the activities taking place in coastal areas, since many species rely on the coastal waters to meet their needs in some way or another. However, the problem is more complicated than this, as pollution is a global worriment. This true extent of pollution can be seen in Greenland sharks. These are deep water animals that prefer the remote locations of the colder seas, and yet even they have been found to possess contaminants. It is also important to remember that pollution need not be chemical in nature; discarded fishing gear and plastics can entangle and injure or even kill sharks and other animals. Whether in the form of a lost toy or a discarded longline filament several miles in length, these objects can be threatening to a wide variety of marine life.
The different threats sharks face, from direct aggression from man to the unintended danger people create through pollution, makes the future of these animals uncertain. Their slow rate of growth and reproduction means sharks cannot easily rebound from such a wide variety of pressures, and several species may soon face extinction. While it is never an encouraging thought for a species to become extinct, what does this really mean for the oceans? What would happen to the marine world should the shark population be eradicated? Among the many things researchers have learned about sharks, from their long history to their diversity, probably the most significant is their role in nature. Sharks are vital to the health of the oceanic ecosystems, and their influence must not be removed from nature.
Sharks are essential to marine habitats in a way that most fish are not. Many shark species are apex predators in most marine ecosystems, keeping the populations of most fish within a healthy range in proportion to their habitat. Sharks are not only at the top of the food chain in most habitats, they have also evolved a very important interdependency with their respective ecosystems. They often target the old, sick, or weak, removing these animals from the population, and thus maintaining the health of the population. By preying on the sick and weak, they prevent the spread of disease and potential deadly outbreaks. Preying on the populations weakest individual also serves to strengthen the population’s gene pool, with mainly the stronger, healthier individuals living on to pass their genes to the next generation. Sharks also maintain the health of ecosystems by scavenging on carcasses. Scavengers are always a very important part of any habitat because they prevent the spread of disease by feeding on the dead bodies they find. By targeting a wide variety of species, sharks control the populations of many marine species and keep them from overpopulating and eventually causing harm to the ecosystem. Since the marine ecosystem consists of many of these intricate food webs, all of which are influenced by sharks, the removal of the dominant predators causes these complex structures to collapse. This means that the loss of the sharks would result in a severe ecological imbalance that would also mean the end for several other species. This eventually leads to economic problems as well. A number of scientific studies show that the decline in shark numbers results in the loss of commercially important fish and shellfish species lower in the food chain, such as tuna, which maintain the health of coral reefs. One particular study in North Carolina showed that decreasing shark numbers led to an overpopulation of rays, which began to negatively affect the population of bay scallops and forced the fishery to close. Eventually, the rays consumed all of their scallop prey, and have since moved on to preying on other bivalves. Sharks can also benefit the economy via ecotourism. This is good not only for the economy but also offers yet another good reason not to kill sharks. In the Bahamas, a single reef shark is worth $250,000 as a result of dive tourism, compared to a one time value of $50 when caught by a fisherman. One whale shark in Belize can bring in as much as $2 million over its lifetime.
So it turns out that sharks can not only benefit the economy indirectly, but also directly by allowing ourselves to become immersed with their world and swim with them in their natural habitat. This allows people to see sharks for what they really are, amazing animals with an important ecological role. They are not the vicious man-eaters the media has falsely led so many to believe, but rather animals which play an essential part in our world. And yet humans kill them. Every day, many sharks are destroyed unnecessarily. In the process of killing them for, say, shark fin soup, we indirectly damage our sources of truly important commercial foods. The consequences of the eradication of sharks are already coming into fruition in some places, and these outcomes will only continue to increase in frequency and severity as more and more sharks are killed. Many species are already nearing extinction, with critically low populations that will not easily be remedied. But it is not too late to save sharks.
Until fairly recently, sharks were not offered very much protection since they were not considered economically important and very little was known about them. There is an urgent need for far greater management and monitoring to be instituted at the national, regional, and international levels in order to spare sharks from extinction. Shark conservation can consist of any one of, or any combination of, three levels; conservation for the sake of the environment and maintaining its balance, conservation for the sake of humanity (where no living creature is allowed to become extinct), and conservation for economic reasons. All three levels are valid and meaningful, but conservation of any kind relies heavily on education. One must realize the severity of the situation; shark populations are being decimated. These animals are being killed in numbers far too great for many species to tolerate for much longer. Whether being killed intentionally for their fins or meat, or accidentally as bycatch, shark populations have plummeted and many species may cease to exist in the near future. Fortunately, more countries are beginning to pass legislation to protect these important animals, and there are currently several conservation and management initiatives and plans which operate on different levels, from international conventions to local laws. There is still much progress to be made in shark conservation, however, as some countries have yet to develop effective management initiatives or evaluate those already in place for sharks.
The shark’s journey has been long and difficult. Sharks have survived competition from some of the most impressive ancient marine creatures as well as several extinction events which claimed entire successful lineages. Yet it seems sharks have been overwhelmed by their modern day predators, humans. Hunted excessively for unsatisfactory reasons and impacted by pollution and habitat loss, sharks are not surviving this new set of threats. Their population numbers are falling critically, and the future of many different species is in doubt. However, there will be severe consequences if sharks are pushed to the edge of extinction. Without sharks, the marine ecosystems will lose some of their most important species and suffer greatly. This critical impact will eventually come to hurt man as well, as the extinction of sharks will also mean the extinction of commercial species which humans depend on for food. The irony of the bloody history between man and sharks is that we need sharks. Sharks are essential for the health of marine habitats and, by extension, are important for mankind as well. Though shark conservation has certainly improved in recent years, more will need to be done for these animals to survive the damage that has been inflicted on their populations. It is vital to learn more about these animals, and strive to maintain their presence in this world. The sharks have graced the marine world for ages, and we need not see them disappear now.
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