 |
Whale Shark
|
More than 400 known species of sharks inhabit the world’s oceans. They vary widely in size and behavior, from the goldfish-sized dwarf dog shark to the whale shark, which can grow to a length of 18 meters (60 feet) and weigh as much as two full-grown African elephants. Many people, influenced by movies, popular novels, and widespread media coverage of shark attacks, think of sharks as people-eating monsters. In reality, the three largest species—the whale shark, basking shark, and megamouth shark—are gentle giants. These plant-eating sharks swim through the water with their mouths open, filtering out and swallowing huge quantities of phytoplankton. Media coverage of shark attacks greatly exaggerates the danger from sharks. Every year, members of a few species such as the great white, bull, tiger, oceanic white tip, and hammerhead sharks, injure 60–75 people worldwide. Between 1998 and 2008, there were an average of six deaths per year from such attacks. Some of these sharks feed on sea lions and other marine mammals and sometimes mistake swimmers and surfers for their usual prey. However, for every shark that injures or kills a person every year, people kill about 1.2 million sharks. This amounts to 79–97 million shark deaths each year, according to Australia’s Shark Research Institute. Many sharks are caught for their valuable fins and then thrown back alive into the water, fins removed, to bleed to death or drown because they can no longer swim. This practice is called finning. The fins are widely used in Asia as a soup ingredient and as a pharmaceutical cure-all. Sharks are also killed for their livers, meat, hides, and jaws, and because we fear them. Some sharks die when they are trapped by fishing lines and nets. According to a 2009 study by the International Union for Conservation of Nature (IUCN), 32% of the world’s open-ocean shark species are threatened with extinction. One of the most endangered species is the scalloped hammerhead shark
 |
| Hammerhead Shark |
. Sharks are especially vulnerable to population declines because they grow slowly, mature late, and have only a few offspring per generation. Today, they are among the earth’s most vulnerable and least protected animals. Sharks have been around for more than 400 million years. As keystone species, some shark species play crucial roles in helping to keep their ecosystems functioning. Feeding at or near the tops of food webs, they remove injured and sick animals from the ocean. Without this service provided by sharks, the oceans would be teeming with dead and dying fish and marine mammals. In addition to playing their important ecological roles, sharks could help to save human lives. If we can learn why they almost never get cancer, we could possibly use this information to fight cancer in our own species. Scientists are also studying their highly effective immune systems, which allow wounds in sharks to heal without becoming infected. Many people argue that we should protect sharks simply because they, like any other species, have a right to exist. But another reason for the importance of sustaining this threatened portion of the earth’s biodiversity is that some sharks are keystone species, which means that we and other species need them.
Comments
Post a Comment