Blue Ocean Institute

Aug 20th
2013

Top Ten Shark Myths Dispelled

Oceanic whitetip, Bahamas. Photo by Lance Jordan.

Written by Blue Ocean Fellows, Demian Chapman and Debra Abercrombie, and by Carl Safina

1. THERE ARE JUST A FEW KINDS OF SHARKS AND THEY ARE ALL BIG.
Fact: Shark species are quite diverse and have very different sizes, shapes, habitats, diets and behaviors. Sharks range in size from the tiny cigar shark (only 6 inches long) to the 45-foot long, gentle Whale shark. There are over 400 described species of sharks, but over two thirds of them are no bigger than about three feet (the length of a skateboard) when they mature. While some sharks are gray, others are brightly colored in beautiful patterns. Sharks inhabit all of the world’s oceans – from coastal waters to the wide open, deep-blue sea – and some can even be found in freshwater rivers and lakes.

2.  SHARKS ARE VORACIOUS PREDATORS OF LARGE PREY.
Fact: Not all sharks have rows of razor-sharp teeth. In fact, some grind their food with flat teeth, and others don’t even need their teeth to eat. The gigantic Whale and Basking sharks sift food out of the water using rake-like gills. They are filter feeders that mainly feed on plankton, fish eggs and other tiny organisms.

3. ALL SHARKS ARE AGGRESSIVE TO HUMANS.
Fact: Some are, but even those that are occasionally aggressive often swim past people while showing no interest. Most sharks would never see a human as potential food and would never attack; actually most are simply too small. Most sharks do like meat but fish, squid, seal, porpoise, or whale make a shark’s perfect meal. Some sharks can go days or weeks without eating at all. Sharks are not hunting humans. Most “attacks” on humans are mistakes due to poor water visibility or are inquisitive bites. This is why there are many more bites than fatalities.

4. WE HAVE DISCOVERED ALL OF THE SHARK SPECIES OUT THERE.
Fact: Several new species of sharks are being described every year. It’s not that they are appearing out of nowhere, it’s just that so few resources have been devoted to studying sharks and exploring parts of the ocean that humans rarely visit, such as the deep sea or isolated islands. Genetic research is really helping scientists with the discovery of these new species. For example, Blue Ocean Fellow Debra Abercrombie discovered a new species of large hammerhead shark while she was doing her graduate studies on the genetics of other well-known species of hammerheads. This new species, the Carolina hammerhead, looked very similar to the widely distributed scalloped hammerhead shark that swims along the Atlantic coast of the U.S.A. However, DNA testing revealed that this hammerhead was genetically distinct—a new species swimming right under our very noses.

5. IF WE STOP “SHARK FINNING” THEN WE WILL PREVENT THE DECLINE OF SHARKS.
Fact: In some countries fishermen still remove the fins from sharks they catch and then dump the rest of the body. This is shark finning. The practice stems from the very low value of shark meat compared to shark fins, which fetch hundreds of dollars per pound in Asian markets. Most of these fins are destined for use in the luxury dish, shark fin soup. Finning has run rampant during the last two decades and remains a problem in some parts of the world. But if all finning stopped tomorrow, the exploitation of sharks for their fins and other products would continue–and at an unsustainable rate in many places. The key to preventing dangerous declines in shark populations is for shark fisheries to be sustainably managed. Unfortunately, very few of them are. Perhaps it is time for the fishing industry to shoulder the burden of proving the catch levels they propose are sustainable before they are allowed to proceed.

6. THE BULL SHARK IS SUPER-AGGRESSIVE BECAUSE THEY HAVE THE HIGHEST TESTOSTERONE LEVELS IN THE ANIMAL WORLD.
Fact: This Shark Week “fun fact” gets dusted off every time a reporter does a story on Bull Sharks. Even some shark researchers are guilty of repeating it. But it is incorrect. The statement is based on an anomalous field measurement taken from one animal. Subsequent testosterone measurements in bull sharks are not unusually high for a vertebrate of their body size. Although potentially dangerous, Bull Sharks are not the roid-raging monsters they are often portrayed to be.

7. SHARKS SPAWN JUST LIKE FISH.
Fact: For most sharks, the reproductive process as a whole is much more similar to humans and other mammals than it is to fish. First, sharks don’t spawn, they practice internal fertilization with males transferring sperm to the reproductive tract of females by way of a modified fin called the clasper. And guess what, guys….males sharks have two claspers! When fish spawn they release millions of eggs into the water column, with the resulting larvae then having to fend for themselves. Very few of the larvae actually make it to adulthood. Compared to that, many sharks would get the “Mother of the Year” award. Females of most species are pregnant for very long periods and transfer tremendous amount of nourishment to their developing young (which are called “pups”). Some female sharks are pregnant for up to two years before releasing their pups.

Mako shark. Photo by Carl Safina.

8. THERE ARE TOO MANY SHARKS IN THE SEA.
Fact: Many shark species are declining due to excessive fishing and/or loss of habitat. The most recent estimates suggest around 100 million sharks are killed by commercial fisheries every year and at an unsustainable rate. Sharks likely play a vital role in determining the structure of marine ecosystems. In some cases, they keep populations of prey species under control by eating some of them and influencing the behavior of the rest. Keep in mind that sharks also help coastal economies through ecotourism, such as shark diving and tag-and-release angling.

9.  ALL SHARKS CAN SMELL BLOOD IN THE WATER FROM MILES AWAY.
Fact: That would depend entirely on how much blood and how many miles! Sharks do have a highly developed sense of smell, which helps them hunt in the dark and detect their prey. Some sharks depend more on eyesight at times, and some depend on detecting electrical impulses of fish hidden in the sand.

10. SHARKS HAVE WALNUT-SIZED BRAINS AND AREN’T VERY INTELLIGENT.
Fact: Sharks can exhibit complex social behavior and some species communicate with body language, live in groups and individual sharks learn from their experiences. Some species navigate between tiny areas separated by thousands of kilometers with remarkable accuracy. Sharks and rays have some of the largest brains among all fish, with brain-to-body ratios similar to birds and mammals.

Top image: Oceanic whitetip shark, Bahamas. Photo by Lance Jordan. Image #2: Mako shark. Photo by Carl Safina.

 

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