Blue Whale

The largest creature ever known to have existed on Earth is the present-day blue whale. Today's blue whale is even larger than its prehistoric ancestors, reaching a total length of 30 m (100 ft.) and a weight of 136 t (150 tn.). Adult female blue whales are larger than adult males. The blue whale's heart alone is the size of a small car! Even the largest dinosaur weighed only about 18 t (20 tn.), although it probably reached 40 m (131 ft.) in length.

The calves measure 7 m (23 ft.) at birth and weigh about 2.2 to 2.7 t (2.4 to 3 tn.). A female blue whale can produce more than 200 litres (50 gal.) of high-fat milk per day. The calf gains up to 4 kg (9 lb.) per hour. When weaned at about six months of age, the calf will already be about 16 m (52 ft) long.

This giant animal is placid and shy. On the ocean surface, its normal cruising speed is about 12 knots, but it is capable of attaining 20 knots in short bursts. The maximum reported depth reached by the species is 194 fathoms. It is capable of remaining submerged beneath the surface for 50 minutes, although 10 to 15 minutes is more typical.

Blue whales have been found in every ocean of the world: Pacific, Atlantic, Indian, Arctic and Southern.

Blue whales comprised about 90% of the whaling industry's total catch during the early part of the 20th century, after the advent of harpoon cannons. In 1931 alone, almost 30 000 of these majestic creatures were killed. By 1966 there were so few blue whales that the International Whaling Commission declared them protected. In 2000 it was estimated that there were fewer than 10 000 left.

source : http://nature.ca, http://www.sbnature.org, youtube

Bull Shark

Photograph by Brian J. Skerry

Bull sharks are aggressive, common, and usually live near high-population areas like tropical shorelines. They are not bothered by brackish and freshwater, and even venture far inland via rivers and tributaries.

Because of these characteristics, many experts consider bull sharks to be the most dangerous sharks in the world. Historically, they are joined by their more famous cousins, great whites and tiger sharks, as the three species most likely to attack humans.

Bull sharks get their name from their short, blunt snout, as well as their pugnacious disposition and a tendency to head-butt their prey before attacking. They are medium-size sharks, with thick, stout bodies and long pectoral fins. They are gray on top and white below, and the fins have dark tips, particularly on young bull sharks.

They are found cruising the shallow, warm waters of all the world’s oceans. Fast, agile predators, they will eat almost anything they see, including fish, dolphins, and even other sharks. Humans are not, per se, on their menus. However, they frequent the turbid waters of estuaries and bays, and often attack people inadvertently or out of curiosity.

Bull sharks currently are not threatened or endangered. However, they are fished widely for their meat, hides, and oils, and their numbers are likely shrinking. One study has found that their average lengths have declined significantly over the past few decades.

Type: Fish

Diet: Carnivore

Average lifespan in the wild: 16 years

Size: 7 to 11.5 ft (2.1 to 3.4 m)

Weight: 200 to 500 lbs (90 to 230 kg)

Group name: School or shoal

Did you know? Bull sharks have been found thousands of miles up the Amazon River, and in Nicaragua have been seen leaping up river rapids, salmon-like, to reach inland Lake Nicaragua.

source : http://animals.nationalgeographic.com, youtube

Goblin Shark

The Japanese fishermen who caught the first specimen of Mitsukurina in the "Black Current" off Yokohama called it tenguzame, which means "goblin shark." This has become its common name, although very few people besides ichthyologists and shark-book authors ever get a chance to use it. The shark is extremely rare, found only in deep water off Japan, South Africa, perhaps off Portugal, and, in one strange instance, in the Indian Ocean, cable malfunction necessitated the raising of the cable, and an awl-like shark's tooth was found embedded in the wire covering. The cable had been at 750 fathoms, and the tooth belonged to a goblin shark.

The shark is thought to have been feeding on some sort of animal life growing on the cable at that depth, but very little else is known of its feeding habits. Its awl-like teeth and protrusible jaws seem to indicate that it is a fish eater, but this is only a supposition. (It probably needs protrusible jaws to feed at all, given the nature of its forehead appendage. This seems a self-handicapping situation, so perhaps the protrusion serves some other, less problematical function.) The first known tenguzame was a 3.5-foot male, but subsequent specimens have been as long as 14 feet.

This seems to me the strangest of all the sharks. It looks like some kind of prehistoric survivor, an experiment in shark design that doesn't seem to work. And yet, by definition, it does work. Triceratops, the dinosaur with three horns, is long gone, as are Pteranodon and hundreds of other "impossible" animals. There is little that can be said about this mysterious shark, because so little is known about it. And yet, we have the most curious, incontrovertible fact of all: Mitsukurina lives.

According to National Geographic Kids: A fourth of the goblin shark's weight can be its liver. Scientists don't yet understand why its liver is so big. These sharks have been found as deep as 4,000 feet. This 10-foot-long shark preys on small octopuses and fish. It has rarely even been seen by people. The shark's "nose" is dotted with sensory cells. Scientists think the snout's main purpose is to help the shark find food in deep, dark waters.

source : http://www.greengoblin.com, Youtube

Great White Shark

Photograph by Brian J. Skerry

Great whites are torpedo-shaped with powerful tails that can propel them through the water at up to 15 miles (24 kilometers) per hour.

The legendary great white shark is far more fearsome in our imaginations than in reality. As scientific research on these elusive predators increases, their image as mindless killing machines is beginning to fade.

Of the 100-plus annual shark attacks worldwide, fully one-third to one-half are attributable to great whites. However, most of these are not fatal, and new research finds that great whites, who are naturally curious, are "sample biting" then releasing their victims rather than preying on humans. It's not a terribly comforting distinction, but it does indicate that humans are not actually on the great white's menu.

Great whites are the largest predatory fish on Earth. They grow to an average of 15 feet (4.6 meters) in length, though specimens exceeding 20 feet (6 meters) and weighing up to 5,000 pounds (2,268 kilograms) have been recorded.

They have slate-gray upper bodies to blend in with the rocky coastal sea floor, but get their name from their universally white underbellies. They are streamlined, torpedo-shaped swimmers with powerful tails that can propel them through the water at speeds of up to 15 miles (24 kilometers) per hour. They can even leave the water completely, breaching like whales when attacking prey from underneath.

Highly adapted predators, their mouths are lined with up to 300 serrated, triangular teeth arranged in several rows, and they have an exceptional sense of smell to detect prey. They even have organs that can sense the tiny electromagnetic fields generated by animals. Their main prey items include sea lions, seals, small toothed whales, and even sea turtles, and carrion.

Found in cool, coastal waters throughout the world, there is no reliable data on the great white's population. However, scientists agree that their number are decreasing precipitously due to overfishing and accidental catching in gill nets, among other factors, and they are listed as an endangered species.

Type: Fish

Diet: Carnivore

Size: 15 ft (4.6 m) to more than 20 ft (6 m)

Weight: 5,000 lbs (2,268 kg) or more

Group name: School or shoal

Did you know? Great whites can detect one drop of blood in 25 gallons (100 liters) of water and can sense even tiny amounts of blood in the water up to 3 miles (5 kilometers) away.

http://animals.nationalgeographic.com, youtube

Hammerhead Shark

Photograph by Brian J. Skerry

Hammerheads are aggressive hunters, feeding on smaller fish, octopuses, squid, and crustaceans. They do not actively seek out human prey, but are very defensive and will attack when provoked.

Hammerhead sharks are consummate predators that use their oddly shaped heads to improve their ability to find prey. Their wide-set eyes give them a better visual range than most other sharks. And by spreading their highly specialized sensory organs over their wide, mallet-shaped head, they can more thoroughly scan the ocean for food.

One group of sensory organs is the ampullae of Lorenzini, which allows sharks to detect, among other things, the electrical fields created by prey animals. The hammerhead's increased ampullae sensitivity allows it to find its favorite meal, stingrays, which usually bury themselves under the sand.

The great hammerhead is the largest of the nine identified species of this shark. It can grow up to 20 feet (6 meters) in length and weigh up to 1,000 pounds (450 kg), although smaller sizes are more common.

Found in temperate and tropical waters worldwide, far offshore and near shorelines, hammerheads are often seen in mass summer migrations seeking cooler water. They are gray-brown to olive-green on top with off-white undersides, and they have heavily serrated, triangular teeth. Their extra-tall, pointed dorsal fins are easily identifiable.

Most hammerhead species are fairly small and are considered harmless to humans. However, the great hammerhead's enormous size and fierceness make it potentially dangerous, though few attacks have been recorded.

Hammerhead populations are not accurately known, but appear stable worldwide, and they are not considered threatened.

Type: Fish

Diet: Carnivore

Average lifespan in the wild: 20 to 30 years

Size: 13 to 20 ft (4 to 6 m)

Weight: 500 to 1,000 lbs (230 to 450 kg)

Group name: School or shoal

Did you know? Hammerheads use their wide heads to attack stingrays, pinning the winged fish against the sea floor.

source : http://animals.nationalgeographic.com

Mako Shark

Photo modified from Sharks and Rays. TC Tricas, K Deacon, P Last, JE McCosker, TI Walker, L Taylor. 1997. Nature Company Guides, Time Life Book Series. Weldon Owen Pty Ltd San Francisco.

The shortfin mako shark is a sleek spindle shaped shark with a long conical snout. This shark has short pectoral fins and a crescent shaped caudal (tail) fin. There is a distinct caudal keel on the caudal base. Its second dorsal fin is much smaller than the first. The teeth are are slender and slightly curved with no lateral cusps, and are visible even when the mouth is closed. There is marked countershading on this shark: dorsally it is a metallic indigo blue while ventrally it is white.

The shortfin mako can grow to lengths of 3.9 meters (13 feet). There is still some uncertainty about its life-span, but it is suspected to reach ages of between 11-23 years.

As one of the fastest sharks in the ocean, this powerful shark can attain burst swimming speeds of up to 35 km/h (22 mph) and can leap clear of the water to heights of up to 6 meters (20 feet). These qualities have made this species a sought after sport fish in some parts of its range.

Diet

The shortfin mako feeds mainly upon bony fishes including mackerels, tunas, bonitos and swordfish, but may also eat other sharks, porpoises and sea turtles.

Reproduction

Female shortfin makos usually become sexually mature at a length of 3 meters. Developing embryos feed on unfertilized eggs in the uterus during the gestation period of 15-18 months. The 4-18 surviving young are born live in the late winter and early spring at a length of about 70 cm, but have no placental connection during development (ovoviviparity). It is believed that females may rest for 18 months after birth before the next batch of eggs are fertilized.

Habitat

Shortfin mako sharks live in tropical and temperate offshore waters. They are a pelagic species that occur from the surface down to depths of 150 meters (490 feet). This shark is seldom found in waters colder than 16 degrees Celsius.

Range

The shortfin mako is found worldwide. In the western Atlantic it can be found from Argentina and the Gulf of Mexico to Browns Bank off of Nova Scotia. In Canadian waters these sharks are not abundant as they prefer warm waters, but neither are they rare. Shortfin makos are often found in the same waters as swordfish as they are a source of food and both fish prefer similar environmental conditions.

Distinguishing Characteristics

• Teeth are visible even when the mouth is closed
• Teeth are long and slender with smooth-edged cusps
• Distinct countershading, dorsally blue and ventrally white
• Moderately short pectoral fins
• Underside of the snout is white
• Lunate tail and caudal keel

source : http://new-brunswick.net, Youtube

Sand Tiger Shark

Photograph by David Doubilet

Despite their rows of ragged teeth and vicious appearance, sand tiger sharks are actually rather docile, usually attacking humans only in self-defense.

Sand sharks, also known as sand tigers and gray nurse sharks, have a deceivingly ferocious look. They are large-bodied and display a mouthful of sharp teeth that protrude in all directions, even when the mouth is shut. Despite this, they are a docile, non-aggressive species, known to attack humans only when bothered first.

Sand sharks are brownish-gray with rust-colored spots on top and white underneath. They have a flattened, cone-shaped snout and a distinctive, oblong tail with a notched, upper lobe that is significantly longer than the lobe below. Individuals range in size from 6.5 to 10.5 feet (2 to 3.2 meters) in length.

Their name comes from their tendency toward shoreline habitats, and they are often seen trolling the ocean floor in the surf zone, very close to shore. They are found in warm or temperate waters throughout the world's oceans, except the eastern Pacific.

Sand tigers are the only shark known to come to the surface and gulp air. They store the air in their stomachs, which allows them to float motionless in the water, seeking prey. They are voracious predators, feeding at night and generally staying close to the bottom. Their staple is small fish, but they will eat crustaceans and squid as well. They occasionally hunt in groups, and have even been known to attack full fishing nets.

Although this species is widespread and is not widely fished for food, it has one of the lowest reproduction rates of all sharks and is susceptible to even minimal population pressure. For this reason, it is listed as vulnerable and is protected in much of its range.

Type: Fish

Diet: Carnivore

Average lifespan in the wild: 15 years or more

Size: 6.5 to 10.5 ft (2 to 3.2 m)

Weight: 200 to 350 lbs (91 to 159 kg)

Group name: School or shoal

Did you know? Sand sharks survive well in captivity, and their large size and menacing appearance makes them an extremely popular addition to public aquariums.

source : http://animals.nationalgeographic.com, Youtube

Threser Shark

Photo modified from Sharks and Rays. TC Tricas, K Deacon, P Last, JE McCosker, TI Walker, L Taylor. 1997. Nature Company Guides, Time Life Book Series. Weldon Owen Pty Ltd., San Francisco.

The thresher shark is characterized by its large upper caudal fin. This tail fin may often be 50 percent of the total length of the shark. It has a short snout and large eyes placed forward on the head. The second dorsal fin is much smaller than the first. The thresher is a strong swimmer and can leap clear of the water. The jaws are small with small, curved sharp teeth without basal cusps or serrations. Colour varies from brown to black with metallic hues from above and irregular white markings on the underside. In Canadian waters sizes have ranged from 3.3 to 5.5 meters (10.8 to 18 feet) long. The maximum size recorded for this species is 6.1 meters (20 feet), however they generally are between 2 to 5 meters (10 to 16.5 feet) in length.

Diet

The thresher shark eats schooling fish, such as herring and mackerel and cephalopods such as squid. The large caudal fin is used to slap the surface of the water forcing fish to form tighter schools; the tail can then be used as a whip to stun or kill the prey.

Reproduction

This shark is ovoviviparous, with the eggs being hatched inside the female, and 2 to 6 live pups being delivered at a size of 1.5 meters (5 feet) long. During development the young may cannibalize their siblings within the uterine chamber.

Habitat

The thresher often swims at the surface of coastal waters. However it can also occur at depths of 350 meters (1,150 feet) or more. The young may be found inshore in shallow water.

Range

The thresher shark is a summer visitor to the Canadian Atlantic region. They have been captured from July to November, but most frequently during August and September. The thresher ranges through all warm and temperate areas of the worlds oceans. Its northernmost range in the western Atlantic is eastern Newfoundland and it ranges all the way down the Atlantic to the West Indies and northern South America.

source : http://www.new-brunswick.net, Youtube

Tiger Shark

Tiger sharks are named for the dark, vertical stripes found mainly on juveniles. As these sharks mature, the lines begin to fade and almost disappear.

These large, blunt-nosed predators have a duly earned reputation as man-eaters. They are second only to great whites in attacking people. But because they have a near completely undiscerning palate, they are not likely to swim away after biting a human, as great whites frequently do.

They are consummate scavengers, with excellent senses of sight and smell and a nearly limitless menu of diet items. They have sharp, highly serrated teeth and powerful jaws that allow them to crack the shells of sea turtles and clams. The stomach contents of captured tiger sharks have included stingrays, sea snakes, seals, birds, squids, and even license plates and old tires.

Tiger sharks are common in tropical and sub-tropical waters throughout the world. Large specimens can grow to as much as 20 to 25 feet (6 to 7.5 meters) in length and weigh more than 1,900 pounds (900 kilograms).

They are heavily harvested for their fins, skin, and flesh, and their livers contain high levels of vitamin A, which is processed into vitamin oil. They have extremely low repopulation rates, and therefore may be highly susceptible to fishing pressure. They are listed as near threatened throughout their range.



source : http://akunidive.com, http://animals.nationalgeographic.com, Youtube

Whale Shark

GENERAL DESCRIPTION

The whale shark is a the biggest shark and the biggest fish. It is NOT a whale. It has a huge mouth which can be up to 4 feet (1.4 m) wide. Its mouth is at the very front of its head (not on the underside of the head like in most sharks). It has a wide, flat head, a rounded snout, small eyes, 5 very large gill slits, 2 dorsal fins (on its back) and 2 pectoral fins (on its sides). The spiracle (a vestigial first gill slit used for breathing when the shark is resting on the sea floor) is located just behind the shark's eye. Its tail has a top fin much larger than the lower fin.

The whale shark has distinctive light-yellow markings (random stripes and dots) on its very thick dark gray skin. Its skin is up to 4 inches (10 cm) thick. There are three prominent ridges running along each side of the shark's body.

This enormous shark is a filter feeder and sieves enormous amounts of plankton to eat through its gills as it swims.

SIZE

Whale shark

A scuba diver above a Whale shark.
The whale shark is up to 46 feet (14 m), weighing up to 15 tons. The average size is 25 feet (7.6 m) long It is the largest fish in the world. Females are larger than males (like most sharks).

TEETH

Whale sharks have about 3,000 very tiny teeth but they are of little use. Whale sharks are filter feeders who sieve their tiny food through their large gills.

DIET AND FEEDING HABITS

The whale shark is a filter feeder that sieves small animals from the water. As it swims with its mouth open, it sucks masses of water filled with prey into its mouth and through spongy tissue between its 5 large gill arches. After closing its mouth, the shark uses gills rakers that filter the nourishment from the water. Anything that doesn't pass through the gills is eaten. Gill rakers are bristly structures (the thousands of bristles are about 4 inches or 10 cm long) in the shark's mouth that trap the small organisms which the shark then swallows. The water is expelled through the sharks 5 pairs of gill slits. The prey includes plankton, krill, small fish, and squid. The shark can process over 1500 gallons (6000 liters) of water each hour.

SOCIAL GROUPS

Whale sharks are solitary creatures. Groups of whale sharks have only rarely been seen.

HABITAT

Whale sharks live in warm water (near the equator) both along the coast and in the open seas. They spend most of their time near the surface.

DISTRIBUTION

Whale sharks are found worldwide in the warm oceans from the equator to about ±30-40° latitude. They are not, however, found in the Mediterranean Sea.

SWIMMING

Whale sharks are slow swimmers, going no more than 3 mph (5 kph). They swim by moving their entire bodies from side to side (not just their tails, like some other sharks do).

REPRODUCTION

The Whale shark was long thought to be oviparous (an egg 14 inches (36 cm) long was found in the Gulf of Mexico in 1953; this would be the largest egg in the world). Recently, pregnant females have been found containing hundreds of pups, so, Whale sharks are viviparous, giving birth to live young. Newborns are over 2 feet (60 cm) long.
Whale sharks are sexually mature at 30 years old. This is the age at which they are able to mate and reproduce.

WHALE SHARK ATTACKS

Whale sharks are harmless to people and usually indifferent to divers.

LIFE SPAN

It has been estimated that whale sharks may live up to 100 - 150 years.

source : http://www.enchantedlearning.com, http://sandynata.files.wordpress.com, Yutube