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Shark Facts Have you ever wondered where would be the best place to go cage diving with great white sharks? Or what kind of shark is the biggest fish in the sea? Here are a few quick shark facts about some of the species most commonly encountered by divers Introduction Fossil evidence suggest that sharks have inhabited the oceans of the world for over 400 million years. However, since their skeletons are composed of cartilage instead of bone, most of the fossil evidence we have regarding prehistoric sharks are the teeth only, not complete skeletons. Their diet consists of a wide range of sea creatures, however all known sharks are carnivores. Their diet consists of everything from fish to birds, to seals, to bottom-dwelling organisms, and even plankton (tiny, shrimp-like creatures that float in the water). Having an unlimited number of teeth that grow and rotate into place to replace lost ones, the diet of a shark can be narrowed down easily by looking to see what kind of teeth it has. Sharks with narrow teeth with needle-like points generally use them to catch and eat smaller prey like small fish, while sharks with large, triangular teeth with serrated edges generally use them to attack large prey, like seals. They clamp down on their prey and then, using the saw-like edges of the teeth, tear out a huge hunk of flesh! The sharks that feed on the tiny plankton are filter feeders,- meaning they open their mouths wide as they swim and allow the vast clouds of plankton in the water to float in. These sharks have tiny, almost non-existent teeth! Habitat and Range As apex predators, sharks have very few natural enemies, and are found in virtually all the oceans of the world. They range in size from only a few inches long to over 50 feet, and are even known to travel far up waterways and even to inhabit freshwater lakes and rivers. From their position at the top of the food chain pyramid, sharks play an important role in removing sick and weakened fish from the marine environment, and their range contains both global, and localized characteristics. For example, it is known that Great White Sharks prefer the cool temperate waters close to rocky outcrops and volcanic islands, where they can usually find a plentiful supply of their favorite food (seals), and where deep water lies close by. In fact, they are known to maintain such a localized home range that shark diving operators typically become so familiar with individual sharks that they are able to recognize them, and see them often enough to give them names based on characteristics such as their aggressiveness, shyness, or based on the cuts and scrapes or other unique colorations they may have on their skin. At the same time, these local populations of great whites contain wanderers, who roam in from the open sea and make only brief appearances, only to disappear and never be seen again. Other sharks, such as sand tigers and hammerheads, congregate together in large numbers during mating seasons, often at predictable times and locations during the spring and fall, only to break up and roam freely as individuals soon after. Ironically, it is this characteristic of a global range habitat that makes international cooperation so important in protecting dwindling shark populations. It does a global species little good to be protected in the waters of one country, only to be freely butchered when they wander into the waters of another. Shark Senses In the surf zone, where swimmers and surfers are sometimes (but rarely) attacked by sharks, it is usually under conditions of limited visibility due to the choppy, murky waters in these areas. Often under these conditions a shark will mistake the flash of a hand or a foot for a fish, or mistake the shadow of a surfboard, outlined against the sky, for that of a large seal or sea-lion. But in the open sea things are much different. Sharks are highly evolved predators, featuring a heightened sense of smell, excellent night vision, as well as the amazing ability to detect even the most minute amounts of electric currents from living organisms. A sharks sense of smell is extremely acute, and is probably its most important sense. Unlike land animals, the nostrils are not used for breathing in any way, and are not even connected to the mouth. Instead, they are completely devoted to smell, and scientists believe that sharks can detect tiny amounts of blood, as small as one drop of blood in 100 gallons of water, from an injured fish. Water continually flows through them, alerting the shark to the possible presence of a wounded or injured animal. And while the ability to detect electromagnetic impulses is believed to be common in many marine organisms, in sharks this sense is believed to be particularly well-developed. They may use it to navigate through the earth's magnetic fields, and their ability to detect electrical impulses may be one reason why some species find it impossible to survive in aquariums. The barrage of electrical impulses in an aquarium may override and confuse their senses. Scientists have even speculated that the hammerhead shark can detect the small electrical impulse emanated from the heart beat of skates and rays hiding underneath the sand! Reproduction Most sharks are viviparous (live-bearing), while others are oviparous (egg laying). In cases of live-bearing sharks, the eggs are fertilized inside the mother shark, and in many species the first shark to hatch will devour its siblings as nourishment. After live birth they have a full set of teeth and are capable of surviving on their own. This is a good thing because often their first mission in life is to escape their own parents who will eat them if they linger too long! The size of a litter may vary from 2 or 3 pups depending on the type of shark, all the way up to 100. Like most large animals with few natural predators, it takes most of them many years to reach sexual maturity. Once they finally do reach an age where they are old enough to reproduce, they bear only a relatively few number of young at a time. These number of total offspring are sufficient to sustain the overall populations under natural circumstances, but not under circumstances of extreme pressure or stress. (This is one of the reasons shark conservation is so important. As animals with very slow rates of reproduction, they are extremely vulnerable to the threats posed by over-fishing.) Some species are believed to mate during certain seasons and times of year, and others are believed to mate all year long, but overall there is much that remains unknown about shark reproduction, but about shark behavior in general. As creatures of the open ocean, there is much about them remains a mystery, and it will no doubt take many years for scientists to even scratch the surface in unravelling the mysteries surrounding these truly awesome, amazing animals!
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Top
Shark Diving
Many
sharks have a global habitat Great White Sharks
It is possible
that no other living creature on the earth has been Hammerhead Sharks
There are several different types
of sharks referred to as hammerheads, for example, there is the Winghead
Shark, the Scalloped Hammerhead, the Great Hammerhead, and the Smooth
Hammerhead, ranging in size from 5 feet up to 15 feet long, with rare
appearances of individuals (in the case of the Great Hammerhead) of up to
20 feet long! Sand Tiger Sharks
The Sand Tiger is yet another
species with an undeserved bad reputation. It's
ferocious reputation is based on the fact that this shark is frequently
guilty of attacks Galapagos Sharks
Few sharks can rival the beauty and
classic shark "form" of the Galapagos Shark. Getting it's
name from it's original discovery in waters off of Reef Sharks
There are several sharks shark
Whale Sharks
The whale shark is the largest
known fish in the sea, reaching a massive size in excess of 40 feet in
length! It can weigh as much as ten tons!
Since they frequently feed in relatively shallow waters around reefs, free diving
or scuba diving with this fish is possible.
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This is your year to meet "Mystery" at Isla Guadalupe
Email us at
staff@divingwithsharks.com or call us anytime 619.565.0208
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