Ruskell 1Caitlyn Ruskell11/18/11Mrs. Tillery Saving Our Sharks Sharks have been swimming in our planet’s oceans for 450 million years,surviving through many of Earth’s mass extinctions. These hardy creatures serve as thetop predators in their marine ecosystems, managing populations all around the world.However, in recent years, humans have taken population management into their ownhands, turning the ocean’s apex predator into prey. The widespread killing of sharks isalready taking its toll, and if more measures are not taken to protect these animals, wemay lose them forever. Before elaborating upon the dangers that sharks face, it would do some good toexplain exactly what makes a shark a shark. All sharks belong to the kingdom Animalia,phylum Chordata, class Chondrichthyes, and subclass Elasmobranchii. To be included inChondrichthyes, a fish must have a skeleton composed only of cartilage, a true upper andlower jaw, and nostrils that lie below the head. To be included in Elasmobranchii, the fishmust also have several adjacent gill slits; however, these are not sharks’ only definingcharacteristics. Most sharks have streamlined, torpedo-shaped bodies, equipped withcollagen-fiber fins used for balance, lift, and maneuvering. Sharks also possess many morphological adaptations that make them well-suitedfor their underwater environment. Sharks have skin made up of millions of tooth-likescales called dermal denticles, that allow the shark to move quickly and efficientlythrough the water by minimizing water resistance (Steinkohl). Their skin is in fact soefficient in the water that the U.S. Navy has used it to model new submarines and NASAhas used it to model the hull of the Space Shuttle (Benchley). The shark’s dynamic
Ruskell 2features are highly important because most shark species are continuously moving. Withthe exception of nurse sharks, which have tiny openings called spiracles that allow waterto pass over their gills while the shark is at rest, sharks can never stop swimming becausethey need a continuous flow of water over their gills so they can absorb the amount ofoxygen needed to stay alive (United Conservationists). Much like humans and other animals, sharks use different types of muscle fibersfor different tasks. In order to keep moving at a moderate pace to breathe when they areresting, sharks employ their outer layer of red muscle, which is powered by stored fat andoxygen in the shark’s blood. The muscle sharks use for speed comes from their thickinner layer of white muscle, which is fueled by the metabolic breakdown of sugars.Because it is not fueled by oxygen, the white muscle provides the shark with huge burstsof power rather than being used for endurance. Since white muscle provides the shark with huge bursts of energy, it is no surprisethat it also gives the shark the power behind its deadly bite. When sharks bite, their topjawbone, which is not attached to the skull, extends out over their food source almostelastically, giving the shark the ability to bite much more than if its top jawbone wereattached. The shark then bites down with tremendous force, shaking its prey and allowingits multiple rows of razor-sharp teeth to saw through flesh and bone (Steinkohl). Alongwith having bodies perfectly designed for life as the ocean’s top predator, sharks use theirsenses to gain an advantage over their prey. In general, most sharks have excellent hearing, some sharks have excellent vision,and all sharks have an excellent sense of touch. Sharks have what is called a “lateral linesystem” of nerves in their body that helps them to feel the tiniest of vibrations (United
Ruskell 3Conservationists). Sharks also have a unique sixth sense known as their electrosense.Underneath the shark’s head lie tiny pores called Ampullae of Lorenzini, which are filledwith a highly conductive gel. These pores allow the shark to pick up on electricalimpulses produced by other organisms in the ocean as well as the electromagnetic fieldsemitted by the surrounding seascape, enabling them to use this sense to hunt andnavigate. Hammerhead sharks have more of these pores than any other known sharkspecies, and this gives them enough sensitivity to detect electrical impulses as small asone hundred millionth of a volt. In order to process such complex signals, a shark must have a complex brain.Research of shark brain function conducted at the University of California in San Diegohas yielded the results that sharks are in fact capable of spatial and social learning.(Houston). These findings directly dispel the myth that sharks are mindless killers, still,people continue to have an irrational fear of sharks. For hundreds of years, people have been terrified of sharks. After the 1975 releaseof Jaws, shark attack stories became popular forms of entertainment, and these storiesseem to flood the media every summer. Stories like these keep beach-goers all over theworld in fear of sharks, even though statistics prove this fear to be irrational. Out of over350 species of sharks, only ten reported species have ever bitten people (UnitedConservationists). Of these ten species, only three, white, tiger, and bull sharks, areresponsible for over half of all shark attacks (Benchley). Most unprovoked shark attacksoccur in areas where visibility is poor, making it easier for a shark to mistake a person fora prey item and go in for a test-bite. More often than not, shark attacks are provoked,meaning that people engage in a shark-attracting activity. Activities like spear fishing,
Ruskell 4and even splashing around in water, are likely to attract sharks. Despite popular belief,more than 90% of shark attacks are nonfatal, and with the cases that are, victims usuallydie from shock or loss of blood rather than being eaten by the shark (Campbell). In 2008,only four people worldwide died from shark-related incidents, while 49 people died fromdog bites and 793 died in bicycle accidents. Sharks cause fewer deaths than bees,lightning, and even bathtubs, yet people still fear them, creating an incentive for humansto hunt sharks (United Conservationists). Every year, more than 100 million sharks are killed in fisheries throughout theworld; 73 million are killed solely for their fins. Shark fins are the most profitable seafood item in the world, and in Asia, particularly China, they are sold to add texture to adelicacy dish known as shark fin soup, selling for up to one hundred US dollars per bowl.The practice of “shark finning,” as it is called, is wasteful and cruel; only 1% to 5% of theshark is actually collected, and many times live sharks are brought on board, their fins areremoved, and the shark is thrown back into the ocean to drown or bleed to death. Whensharks are not specifically hunted for their fins, they often fall victim to bycatch, orunintended catch. Fisheries that cast long-lines are responsible for killing tens of millionsof sharks in bycatch every year, and many more cases of bycatching sharks goundocumented. Fisheries involved in shark finning and long-line fishing have depletedthe world’s shark population by 90% in some areas, making sharks the largest group ofthreatened marine species according to the World Conservation Union (Griffin). Killingsuch massive amounts of sharks at a time is devastating to the shark population. Mostsharks are slow growing, they take many years to reach sexual maturity, their gestationalperiods are long, and they only produce a few offspring at a time, whereas other fish
Ruskell 5species can produce thousands of offspring in a very small time frame, making sharkpopulations very sensitive to over-fishing (Benchley). If the shark population isdevastated, ecosystems will crumble as a result. According to Rob Stewart, the star, narrator, director, and producer of the award-winning documentary Sharkwater, sharks are “the one animal we fear the most,” and“the one we can’t live without.” (Stewart). In ocean ecosystems, sharks keep populationshealthy by consuming sick and dysfunctional animals. They also keep populationsflourishing by keeping the population density controlled, maintaining the balance ofresources within an ecosystem. Once sharks are removed, a series of chain reactions,called a “cascade effect”, occurs. For example, on the east coast of the United States,populations of great sharks, white, thresher, and great hammerhead, have dwindled to thepoint where they no longer function as a population-controlling device. As a result, rayand sea skate populations have increased dramatically, and they are rapidly depleting thescallop, oyster, clam, and other bivalve populations. Without these bivalves present tofilter the water, rapid algae growth is occurring, which will eventually cause the wholeecosystem to choke. The absence of these organisms also has adverse effects on the U.S.Economy; lack of scallops has caused the North Carolina fishery to shut down and thedepletion of Quahog populations on the northern part of the east coast has put animmense strain on businesses who sell clam chowder. Other ecosystem degradation hasbeen seen in the Caribbean, where the removal of sharks has caused grouper populationsto drastically increase. Grouper eat the small fish that graze on the microalgae that livesinside of coral, and when the microalgae is no longer eaten by these fish, it grows out ofcontrol killing coral, decreasing the biodiversity of the reef, and making it less resilient to
Ruskell 6environmental changes. Due to the adverse effects of shark removal in the Caribbean,45% of coral had been destroyed in less than twenty years (Griffin). Along with causingadverse effects in the ocean, the elimination of sharks could eliminate chances of curingheart disease in humans, finding preventative treatments for immune deficiencies, andgaining further understanding of our neurological abilities (Discovery). Clearly, theremoval of sharks from our oceans adversely affects people all over the world. Since there is no legal limit to the amount of sharks a person can kill in the openocean, sharks everywhere continue to go unprotected. Fortunately, some people areworking to change this. Many organizations have pushed for legislation protecting sharksin the United States, and thanks to the Shark Conservation Act of 2010, shark finning isnow illegal in the United States. Shark finning is still a problem everywhere else in theworld, and today researchers at the University of Miami spend their time tagging sharksin order to study their migratory patterns, in hopes that a world network of protectedareas can be established for sharks (Katayama). Groups of inspired shark attack survivorsare even pushing the United Nations to create legislation that would illegalize sharkfinning throughout the world (Rand). If efforts are continued, the idea of a world withouta shark finning industry may become a reality. All in all, sharks are worth more alive than dead. These perfectly evolved animalskeep ocean ecosystems thriving, they inspire our vehicles and technology, they teach usabout ourselves in many ways, and they fuel economies throughout the world, a singleshark being able to bring in hundreds of thousands of dollars in dive tourism revenueduring its lifetime (Stewart). If sharks are eliminated from the planet, devastating effectswill occur in ocean ecosystems, and these effects will drastically change humans’ way of
Ruskell 7life forever. Luckily, there is still hope for these ocean dwellers, and by spreadingawareness of their importance and their vulnerability, a brighter future may be in store forthe shark.
Ruskell 8 Works CitedBenchley, Peter. The End of The Line? N.p.: n.p., 2007. SharkWater.com. Web. 12 Aug. 2011. <http://www.sharkwater.com/downloads/pdfs/ WildAid_Shark_Report2007.pdf>.Campbell, Ernest, MD, FACS. “Sharks.” Scuba-Doc.com. Ernest Campbell, 2010. Web. 15 Nov. 2011. <http://scuba-doc.com/shrks.htm>.Griffin, E., et al. Predators as Prey: Why Healthy Oceans Need Sharks. Oceana.org. Oceana, July 2008. Web. 13 Nov. 2011. <http://na.oceana.org/sites/default/ files/o/fileadmin/oceana/uploads/Sharks/ Predators_as_Prey_FINAL_FINAL.pdf>.Houston, Rodd, narr. Shark Superhighway. Thomas Lucas. National Geographic. 2008. Television.Katayama, Lisa. “Cool Job: Deep Sea Videographer.” O The Oprah Magazine 15 Sept. 2011: n. pag. Oprah.com. Web. 13 Nov. 2011. <http://www.oprah.com/blogs/ Cool-Job-Deep-Sea-Videographer>.Rand, Matt. “Director of Global Shark Conservation at the Pew Charitable Trusts.” Press Conference with the United Nations. New York, New York. 13 Sept. 2010. pewtrusts.org. Web. 13 Nov. 2011. <http://www.pewtrusts.org/uploadedFiles/ wwwpewtrustsorg/News/Press_Releases/Protecting_ocean_life/ Sharks%20press%20conference%209-13-10_930.mp3?n=5732>.“Shark Education.” UnitedConservationists.org. United Conservationists, 2011. Web. 14 Nov. 2011. <http://unitedconservationists.org/ index.php?option=com_content&view=article&id=125&Itemid=243>.
Ruskell 9Steinkohl, Gary. “What Makes A Shark A Shark?” Sharksaver.org. Shark Savers Inc., 2011. Web. 14 Nov. 2011. <http://www.sharksavers.org/en/education/shark- biology-behavior/396-what-makes-a-shark-a-shark.html>.Stewart, Rob, prod. Sharkwater. Alliance Films Inc., 2008. Film. “20 Ways Sharks Can Help Humans.” Discovery.com. DiscoveryCommunications, 2011. Web. 13 Nov. 2011. <http://dsc.discovery.com/sharks/top-20/ways-sharks-can-help-humans.html>.