By Neal Lineback and Mandy Lineback Gritzner, Geography in the NewsTM and Maps.com
As families head to the beaches for vacation each summer, some may secretly fear the presence of one of the fastest and most dangerous fish in the ocean—the great white shark—the largest predatory fish in the world.
The 1975 Steven Spielberg film “Jaws,” starring Roy Scheider, Robert Shaw and Richard Dryfuss, did a great deal to strike the fear of great white sharks in the general public. Ranked as the 56th greatest film ever made by the American Film Institute in 2008, “Jaws” remains a classic horror film.
A pair of huge white sharks have been tagged electronically by Ocearch Global Shark Tracker and can be followed online. “There’s a 3,546 pound shark named Mary Lee swimming through murky waters right off the Long Island coast. Read more: Among the dozens of researchers and scientists all over the globe who are monitoring Mary Lee’s every move is 68-year-old shark enthusiast Jo O’Keefe,” according to Carol Kuruvilla, New York Daily News, Jan. 31, 2013.
Despite having the “silver screen” reputation as a man-eater, however, great white shark attacks are quite rare. Its victims often survive, suggesting that this shark finds human flesh objectionable. Scientists question whether great whites are actually confused when they attack humans, mistaking their shadows for seals or other large prey.
The great white is found in temperate oceans, preferring a temperature ranging between 54 and 75 degrees F (12 and 24 degrees C). The shark lives off the coasts of North America, southern Africa, Australia (especially New South Wales and South Australia), New Zealand, Japan, Chile and parts of the Mediterranean. One of the densest known great white shark populations lives around Dyer Island, South Africa, which makes the area a prime shark research location. Great white sharks are rare in both polar and tropical waters.
Great white sharks are large, averaging between 5,940 and 7,040 pounds (2,694 and 3,193 kg) and 12-20 feet (3.7-6 m) in length. The female is usually larger than the male. Its shape resembles a torpedo with a pointed tip, making this predator extremely fast in the water and amazingly efficient.
When the great white finds prey, it uses its 3,000 teeth situated in three rows to rip and tear the flesh. It does not chew its food, but swallows chunks of its prey whole. The shark can survive for up to two months without food.
The great white shark has numerous adaptive detectors used for hunting. It can monitor tastes in the water and detect changes in pressure and electrical activity. Like other fish, the great white has pressure sensors called a lateral line system. At close range, this system allows the shark to “feel” the pressure generated by moving prey. It can also see well despite limited underwater light. At an even closer distance, the great white can sense small electrical pulses coming from its prey.
Recent scientific evidence shows that great white shark numbers in the northeast Pacific Ocean are far fewer than previously thought. The International Union for Conservation of Nature (IUCN) lists the great white shark as “vulnerable.”
In recent years, global shark species in general have suffered steep declines. Scientists estimate that as many as one-third of the world’s sharks and other cartilaginous fishes are threatened. On the United States’ eastern seaboard, shark numbers have plunged, some as much as 90 percent. Environmental groups estimate that about 73 million sharks are killed globally each year.
Although sharks are rarely targeted for their flesh, commercial and recreational fishermen take them for their jaws, teeth and fins, or as trophy fish. Great white sharks that are taken during the long period between birth and sexual maturity (about 15 years) never reproduce, hindering population expansion.
The Bahamas passed a law to protect its shark species in 2011. The country has banned shark fishing in its waters, successfully converting all 243,000 square miles (630,000 sq. km) of the country’s territorial waters into a shark refuge. The Bahamas will prohibit the sale, import and export of shark products, many of which previously went to China. The demand for shark fins in China is particularly high as they are used in a popular Chinese soup.
Very little shark flesh is consumed. Many are killed only for their fins. Until humans cease killing threatened shark species, their numbers will likely continue declining. Bans like the one implemented in the Bahamas can help shark recovery.
Although the movie “Jaws” fueled a panic about aggressive great white sharks, the true facts are that attacks are few. Being injured in an auto accident on the way to the beach is far more likely than a shark attack. On the first warm day, let’s go swimming!
And that is Geography in the NewsTM.
Sources: GITN 1104 Great White Sharks, Aug.3, 2011; MCMXCVII International Masters Publishers AB. Wildlife Explorer, “Great White Shark,” Card 7; and http://www.bbc.co.uk/news/world-us-canada-14040902
Co-authors are Neal Lineback, Appalachian State University Professor Emeritus of Geography, and Geographer Mandy Lineback Gritzner. University News Director Jane Nicholson serves as technical editor.
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