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Role of Sharks in Marine Ecosystems

Info: 2363 words (9 pages) Essay
Published: 11th May 2021 in Environmental Studies

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There is a kind of fish in the water, and people called it as the king of the ocean which is shark. In fact, everyone knows about sharks, but some people may not have seen them. Sharks as the king of the ocean, they can be said to have almost no natural enemies in the ocean. Moreover, sharks are considered by some to be the most ferocious or fierce, enormous, and scary animals in the ocean because they eat other kind of animals in the ocean or even sea birds. Nevertheless, there are a lot of stories, movies, novels, cartoons, and so forth which describe the sharks as vicious and terrifying ‘‘ocean killers.’’ People will see scenes of sharks eating or attacking people in the movies. In fact, not all sharks are terrible ocean killers because there are different species of shark. In other words, among the many types of sharks, only a very small number have attacked humans. Most sharks are gentle large fish or gentle small fish, but they are slaughtered in just a few decades. The source of the disaster is just a bowl of shark fin soup. TS

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Sharks are fish, of course, they live in the ocean depths of 2,000 meters (6,600ft). Sharks existed on Earth 300 million years before the appearance of dinosaurs, and they have been more than 420 million years ago, and they have hardly changed in the past 100 million years. Sharks belong to the group of elasmobranch fish with fins like a shape of fans, and they are able to live for 20 to 30 years.  The body is thick and short, and the head is nearly square. The eyes are small, oval, and superior. The nostrils have nasal grooves. The mouth is flat and horizontal with developed upper and lower lip folds. Also, they rely on gills to breath. However, they are not like other fish because they have 5 to 7 pairs of grills, and the other bony fish only have a pair of grills. Besides, other fish have hard bones, while sharks do not have hard bones. They have a substance called cartilage to support their body.  Sharks can be up to 6 meters long, weight more than 300 kg, and has a bite force of 400 kg.  It can bite through a 5 cm thick iron plate without any effort. Sharks are not only very fierce, but they are numerous and also very diverse. There are more 500 species of sharks distributed in all oceans around the world.  The largest known shark is over 18 meters in size, and the smallest one is only 18 cm in length.  Nevertheless, in the ancient times, sharks are known as sea dogs, and the etymology of the name ‘‘shark’’ is uncertain. It does not come from a specify name.

There is another shark that is even more surprising! That is the megalodon, which unfortunately has been extinct for more 23 to 3.6 million years ago. It has an exaggerated size of nearly 20 meters and a streamlined body. It just looks like a small submarine, and this shark’s bite force is known the largest bite force among creatures in the world. Its bite force is about 20 tons.  Nonetheless, there is a difference of shark from other fish, and it lies in their breathing. Other fish species first suck seawater into their mouths and wash the blood vessels through the hairs in their mouths. After absorbing the air, spit out the sea water. Sharks move seawater through the capillaries in the gills to absorb the air in the seawater and transmit it to various organs.  If a shark does not move forward or does not move, it means that the shark is “dead.”

Nevertheless, sharks are at the top of the marine food chain. They grow slowly and often take 20 years or more to reach sexual maturity. At the same time, its pregnancy period is longer, usually as long as 10-12 months, and some even as long as 22 moths, and can only give birth to a few at a time. A mother shark can give birth to 2 to 100 babies per reproductive cycle, but the mother shark does not take care of them. During the embryonic period, shark eggs will become the target of various small fish attack, which is the most delicious foods in their eyes.  Sharks can lay numerous eggs, but very few of them can really grow up, and most of them are swallowed by other fish.  However, shark embryos are not completely incapable of protecting themselves. They have the ability to feel threats from outside world. For example, if a predator approaches them, they will pause their breathing, trying to make themselves appear silent. Also, the baby sharks swim and hurst as soon as they are born. In other words, after they are completely transformed to sharp from the shark egg, they stand on their own and face the danger of being eaten. They depend on themselves. After one reproduction, it is often not possible to reproduce again after a year or even several years. Even though shark can reproduce a lot in a time, their reproduction speed and growth rate are extremely slow.

Sharks have a particular sense of smell, and it is the most sensitive organ of shark. As long as an animal bleeds in the water, they can come from a few kilometers or even dozens of kilometers away.  In other words, they can smell very fine things from miles away and track the source. They can, for example, easily smell the smells they fear or dislike, the smell of blood and rotten fish melts into the water, even if it diluted to one part per million, they are able to smell. Similarly, even the smell of fluids people excrete that contain one part of 80 billion in seawater, they can be smelled by shark. They mainly attack the gill or neck of the prey, because there is the location of the large artery caused the prey to lose too much blood and died quickly. Nevertheless, they can also feel the vibrations caused by fish or ocean animals 600 feet away be the sensing effect of the mechanical body.  In addition, they have a intensify olfactory system. They have a sensory power, through which sharks can perceive the weak electric field a few around an object.

In the past, it is generally believed that sharks never sleep because they are always active and keep swimming, as if they never need to rest; however, they do sleep but depend on the species.  The way shark sleep is different form the way of other animals, including humans, sleep.  when the shark is sleeping, only one of the left and right brains is resting. In other words, when the shark’s left hemisphere is resting, their right hemisphere will continue work; and when the right hemisphere is resting, their left hemisphere will continue to work. This allows their left and right hemispheres to rest alternately, and they can continue to move while they are sleeping. Since sharks do not have eyelids, people cannot tell from their appearance that they are sleeping or not. They do not have a powerful brain like dolphins that can rotate between the left and right brains. They rely entirely on the low-level neural reflexes of the spinal cord. Therefore, sharks will be slower to external stimuli when they swim unconsciously and cannot reach the level of dolphins.

 Besides, humans are afraid of sharks, but at the same time, the biggest enemy of sharks is humans.  In fact, sharks are not the enemy of humans, they are actually afraid of humans, they are quite timid and rarely attack humans. On every year, only around five people being killed by sharks. In comparison, 200 people are killed by elephants and tigers, and 2,400 people are executed by humans themselves and die of drugs. There are 22,00 people, nearly 1.2 million people died of car accidents, and 9 million people died of starvation each year.  Elephants and tigers are protected, but sharks are being killed because of the abominable shark fin trade. There are an estimated 100 million sharks are killed by fisheries every year. People kill them in the purpose to get the shark fins, which is the filamentous cartilage in the shark fin, because they think shark fines have high nutrition and vitamins but not their meat. For example, there is a custom among wealthy families in China where people use shark fin to add flavor to the soup.  Nevertheless, the development of this custom take advantages of the current shark fin soup, and it has become many dishes for the Chinese National People’s Congress banquet.  In other words, it becomes a common food for millions of people and one of the most economically valuable trade products in the world. People think that shark fins are precious and nourishing, but in fact, the highly sought-after shark fin is not a premium supplement as people think.  First, shark fin does not have special nutritional value. The main ingredient of shark fin is collagen; however, collagen lacks tryptophan and cysteine and is an incomplete protein. Also, scientists have done some experiment. After testing a bowl of shark fin compared with a bowl of egg custard. The protein and nutrition of egg custard are much higher than the shark fin.  Om other words, the nutritional value of shark fin is not high, and it is not as good as eggs, and milk and meat that contain complete protein.

 Nowadays, fisherman know that shark fin value a lot of money because shark fin has been regarded as the best nourishing food, a symbol of high-end and luxury, and they are expensive.  The price of shark fin is about 100 dollars per pound, and even 500 dollars. And the price of each bowl of shark fin soup is between 120 to 200 dollars. Fisherman cut off their fins and throw the living shark body into the sea in where the shark will lose its balance and loss swimming ability and sink to the bottom of the sea to starve to death. This such killing has reduced the numbers of sharks by 90%, and once the shark is extinct, there is no other control by natural enemies.  Without sharks, marine life or the population below the food chain will inevitably increase in number.  Resulting in a large reduction in marine plankton, and 70% of the earth’s oxygen. And this reduction of marine plankton will lead to a sharp increase in global carbon dioxide and an increase in the greenhouse effect, which will lead to changes in the global environment. In other words, the reduction of sharks plays a vital role in the marine environment and even the environment of the earth.  Moreover, the ocean is the most important ecosystem on the planet, which plays a role in a regulating the climate and providing food for other organisms. Therefore, saving sharks is actually saving humans. Perhaps, people are always misunderstood that sharks are actually not that ferocious, and they have no reason to be killed. When they attack humans, most of them just treat humans as seals or fish they like to eat. They are now facing the end of the disaster, and they are an indispensable link in the marine life.

 In addition, sharks are very cruel, but they will not hurt people easily, except for self-defense. Even though they eat a lot food, including fish, turtles, seabirds, sea lions, and debris leave on the ship, they play a role in protecting the marine ecological chain.  As an ancient species, sharks are not only an adaptor to the evolution of the earth, but also a maintainer of marina ecosystem. Sharks mostly feed on small marine life, which helps control the overproduction of small fish.  It drives out and predates the old, weak, and sick fish, and also improves fish genes and populations. Hundreds of cannibal sharks attack humans only when they are extremely hungry. However, there is a kind of known the garbage cans of the ocean which is the tiger sharks.  They often eat dead creatures and garbage, which ensures the cleanliness of the ocean and reduces the spread of the virus. In other words, they have been documented consuming waste such as bottles, cans, license plates, plastics, rubber tires, and so forth.

 To conclude, sharks play a pivotal role in protecting the balance and health of marine ecosystems, but they are high-level consumers or even top consumers in the marine food chain.  Because of this, sharks are on the verge of extinction this extinction of this species will directly lead to a crisis of marine ecology. And it is humankind who suffer a greater disaster in the end. Sharks affect not only the ecosystem, but also the entire marine food chain. Therefore, if people want to truly prevent sharks from being slaughtered and protect the ecosystem, people should be compassionate and reduce appetite, and abandon this bad habit as well.  The increasing demand for shark fins is the main reason why the number of sharks has fallen sharply and is endangered. This family that has left a glorious history on the historical stage has come to an end. People should protect this strange creature.

References

https://en.wikipedia.org/wiki/Shark

https://en.wikipedia.org/wiki/Megalodon

https://usa.oceana.org/blog/shark-fact-friday-14-iron-stomach

https://ocean.si.edu/ocean-life/sharks-rays/sharks

https://ocean.si.edu/ocean-life/sharks-rays/shark-finning-sharks-turned-prey#:~:text=One%20way%20that%20humans%20hunt,it%20back%20into%20the%20ocean.&text=Shark%20fins%20are%20tempting%20targets,high%20monetary%20and%20cultural%20value%20.

https://www.thewanderingrv.com/car-accident-statistics/#:~:text=Nearly%201.25%20million%20people%20are%20killed%20in%20car%20accidents%20each,young%20adults%20ages%2015%2D44.

 

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