Monday, December 19, 2011

Zebra Shark

The Zebra Shark
 Stegostoma  fasciatum

The zebra shark is know for its beautiful markings. There are no attacks on humans by a zebra shark on record.

The easiest way to identify a zebra shark is by its unique markings. When it is young it has striped markings (hence the name zebra shark). As they get older, the stripes break into spots. Sometimes the spots will make the outline of the stripes, such as in the picture above. The coloration in juveniles is dark brown with tan or pale yellow stripes. Adult coloration is tan to pale yellow with black to dark brown spots. The zebra shark has 5 gills on each side. It has a broad elongated upper lobe of the caudal fin, and almost no lower lobe. It has small eyes and a small mouth with barbels on both sides of its mouth.

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Chondrichtyes
Subclass: Elasmobranchii
Order: Orectolobiformes
Family: Stegostomatidae
Genus: Stegostoma
Species: fasciatum

Similar Species and Other Family Members:
The zebra shark is the sole member of the Stegostomatidae family. This shark is very distinctive, but as it is sometimes called a leopard shark, it is often confused with a cold water species which is also called the leopard shark (Triakis semifasciata).

The zebra shark is oviparous (lays eggs). They will lay one to four eggs a brood. Their size at birth is around 25 centimeters (9.8 inches).
A young zebra shark
The maximum length of the zebra shark is 350 cm (11.5 feet).

The zebra shark feeds on shellfish, crustaceans, and small fishes.

Zebra shark jaws
Habitat and Distribution:
The zebra shark lives in the warm waters of the tropical western Pacific and Indian Ocean.

Life Span:
The zebra shark's life span is believed to reach up to 30 years in the wild. The longest known life span in captivity is 25 years.

Conservation Status:
The zebra shark is listed as vulnerable.

A video of a zebra shark I took at
Discovery Cove.

Note: I do not own any of the still images. 

Friday, December 9, 2011

The Whale Shark

Whale shark (Rhincodon typus) with a diver
The Whale Shark is the worlds largest shark. It will occasionally hit a diver with its tail on accident, but other than that it is mostly harmless to humans.

 The easiest way to identify a whale shark is by its massive size.  It is the largest fish in the ocean. It has dark greenish to brownish gray skin covered with white or yellowish spots and irregular dark and light bars. It has a huge mouth that can reach 4 feet (1.4 meters) wide.  The mouth is in front of the head, instead of below the head like it is in most sharks. It has 5 gills and small eyes.

Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
Class: Chondrichtyes
Subclass: Elasmobranchii
Order: Orectolobiformes
Family: Rhincodontidae
Genus: Rhincodon
Species: typus

Similar Species and Other Family Members:
The whale shark is the only member of the family Rhincodontidae.  Its massive size and  striking markings make it easy to distinguish from other sharks.

The whale shark is ovoviviparous (the eggs are nourished by a yolk, but the mother keeps them inside her body until they run out of food from the yolk and then they are born live). Their size at birth is 21 to 25 inches (55 to 64 centimeters). Whale sharks are sexually mature at 30 years. It is thought that one brood can contain up to 300 young!
A man holding a young whale shark.
The whale shark can reach lengths of up to 45 feet ( 13.7 meters)! It can weigh up to 30 tons (33 metric tons).

 The whale shark lives mainly on plankton, but will also eat small squids and bony fishes.

Here is a good image of  whale shark teeth. 

Habitat and Distribution:
Whale sharks are found in warm waters all around the world. They are not, however, found in the Mediterranean Sea. Large populations of whale sharks are often found near Ningaloo Reef, Australia.

Life Span:
The whale shark may live up to 150 years.

Conservation Status:
The whale shark is now listed as a threatened species.

note: I do not own any of these pictures

Thursday, December 8, 2011

The Goblin Shark

Goblin shark with jaw protruding.
Goblin shark with jaw in normal position.

Common name:
 Goblin  Shark.
Scientific name:
 Mitsukurina owstoni

The goblin shark is a very rare, deep water specimen. It is not a threat to humans, since it lives at depths that humans can only visit via submarine.

This unmistakable shark's most recognizable feature is its long, paddle-like snout. The snout's use is unknown, but some scientists believe it allows the shark to have more ampullae of Lorenzini, therefore making its sense of electroreception stronger. Goblin shark juveniles are white to pinkish light gray dorsally and white below.  Adults are pink to light tan, and preserved specimens are gray. The jaw is able to protrude very far. Their skin is soft and flabby. Goblin sharks have 5 gills on each side, two dorsal fins, no fin spines, no nictitating membranes, and their mouths are behind their eyes.

Kingdom : Animalia
Phylum : Chordata
Subphylum : Vertebrata
Class : Chondrichthyes
Subclass :  Elasmobranchii
Order : Lamniformes
Family : Mitsukurinidae
Genus :  Mitsukurina
Species : owstoni

Similar Species and Other Family Members:
The goblin shark is the only member of the Misukurinina, and their are no other species similar to it.

Very little is known about this subject when it comes to goblin sharks. They are believed to be ovoviviparous (the eggs are nourished by a yolk, but the mother keeps them in her body till they run out of food from the yolk and then they are born live).

Goblin sharks are thought to grow from 6 to 15 feet (180 to 450 cm) long. They may reach over 400 pounds (180 kilograms) in weight.

Very little is known on this subject, but we do know they will eat bony fish, squid, and crustaceans. We do not yet know of anything else they will eat.

Teeth & Jaws:
Here is a good illustration of a goblin shark tooth.

When a goblin shark bites prey, it's jaw protrudes out. This gif shows this action excellently.

Habitat and Distribution:
The goblin shark is a deep water species, found at depths of up to 3,940 feet (1,200 meters). It is found in the western Pacific Ocean, the western Indian Ocean, and the western and eastern Atlantic Ocean.

Life Span:
No one knows the life span of the goblin shark.

Conservation Status:
Data deficient.

note: I do not own any of these pictures. 

Friday, December 2, 2011

Save the Sharks

Right now, you're probably thinking, "Why should we bother saving sharks? They are mindless killing machines, out to hunt us." That's not true. Sharks are dangerous, that is true. But so are big cats. They are both smart, deadly, and dangerous predators. Most often the cause of a shark bite is that they are trying to see if we are edible. When they realize we aren't dinner, they swim away to find something else. Sharks are naturally curious but they, unlike humans, don't have hands to feel so they use their mouth. Unfortunately a small bite from a big shark can be deadly. But don't let this keep you out of the water! In truth, you are more likely to die from food poisoning than from a shark attack!

Now let's talk about how sharks help us. Without sharks, the ocean would be a big mess. Sharks eating carcasses helps keep the oceans carrion free and their hunting helps prevent over population. If, for example, white sharks went extinct. The seal colonies wouldn't have as many predators, so they would start to grow. Interbreeding and cramped spaces would cause illness. The sharks would have normally picked of the sick ones. Slowly the seals would eat all the available food and the chain of events would cause the food web to fall apart.

Okay, now that we have established why we need to save sharks, what exactly do we need to save them from?  The simple answer to that is humans. While sharks kill at the most 100 people a year, we kill over 7 million sharks a year! Sharks are apex predators so their slow reproductive rates can't keep up with this massive slaughter. Some sharks are killed for their jaws, liver oil, skin, teeth, and meat, most are killed for shark fin soup. This delicacy is most popular in China and Japan. It can cost up to 100 dollars a bowl! This soup is viewed as a social status; if you can afford it you are upper class. I have heard it isn't even that good!

To get the fins, finning vessels go out to sea and capture any shark they can.  Then they cut the fins off of the shark, sometimes while it is still alive and then throw the shark back into the ocean to die. This is a truly barbaric practice.

Sharks have been around since before the dinosaurs. There is no need for them to disappear for soup!

note: I do not own any of these pictures.

Friday, May 6, 2011

Shark Basics

Shark. A name that sends most people running, or swimming, for cover. But, what exactly is a shark?
Are sharks fish? Do they have bones?
Sharks are fish and they are in the cartilaginous fish family, a.k.a the Chondrichtyes. This means that, instead of bones, sharks have cartilage for every "bone" in their body except their teeth and jaws. Other members of the class Chondrichthyes are the rays, skates, and chimaeras.

How many types of sharks are there?
There are eight orders of sharks. The Hexanchiformes, the Squaliformes, the Pristiophoriformes, the Squantiniformes, the Heterodontiformes, the Orectolobiformes, the Lamniformes, and the Carcharhiniformes. In total, there is believed to be over 400 shark species.

A chart of all shark orders.

How long have sharks been around?
Fossil records show that sharks have been swimming in the seas for over 400 million years. That's about 175 million years before the dinosaurs! Since then the basic shark design has barely changed.

How long do sharks live?
Some sharks are so rare or just cannot be kept in captivity long enough that their longevity is still unknown. Their longevity also depends on the species of shark. Some sharks such as the smooth dogfish (Mustelus canis)  may only live 16 years, where as the porbeagle shark (Lamna nasus) may live as long as 46 years. The whale shark (Rhincodon typus) is thought to live to 100 years.

What does shark skin feel like?
Shark skin feels exactly like sandpaper. It is made up of tiny teeth-like structures called placoid scales, also known as dermal denticles.

Do sharks sleep?
It was once believed that sharks had to keep swimming to breath and could not sleep for more than a few minutes at a time. While some sharks do need to keep swimming, some species, such as the nurse shark (Ginglymostoma cirratum) use spiracles to force water over their gills allowing for stationary rest. Sharks do not sleep like humans, instead they have active and restful periods.

Can sharks hear?
Sharks have an excellent sense of hearing, though you can't see their ears since they have inner ears instead of big, non-streamlined, outer ears like humans have.

How many teeth do sharks have? 
Sharks can have up to 7 rows of teeth in their mouth at any one time. This is so they can lose a tooth and one will be right there to take its place. This way the shark is always ready to attack.

What is "electroreception"?
Electroreception is the sharks sixth sense. It's also the rarest animal sense. Only sharks and the duck-billed platypus of Australia are thought to have this sense. Here's how it works: All organs emit electrical signals. Sharks have special organs called the ampullae of Lorenzini that can detect these electrical signals. This allows sharks to pinpoint and locate the electric field- even if it's coming from an animal buried motionless on the seabed. The ampullae are delicate, jelly-filled pores on the snout. They are so sensitive they can detect electrical fields of one hundred-millionth of a volt.

I hope that answered all your sharky questions!

note: I do not own any of these pictures.

Monday, May 2, 2011

Items Found in the Stomachs of Tiger Sharks

This is a list of items which have been found in Tiger Shark stomachs.

  • aluminum foil
  • aluminum soft-drink cans
  • armor
  • bag of money
  • bag of potatoes
  • beer bottles
  • black cat
  • boat cushions
  • boots
  • brass casing from a 18-pound (8-kilogram) shell
  • burlap sacks
  • cattle bones and hooves
  • chicken coop
  • chickens
  • cigarette tin
  • conch shells and opercula
  • cows
  • deer antlers
  • driftwood
  • driver's license
  • dogs
  • donkey parts
  • drums
  • empty wallet
  • explosives
  • fabrics
  • finger ring
  • grass
  • head and forequarters of a crocodile
  • hind legs of sheep
  • horse parts
  • horseshoe crab
  • human parts
  • hyenas
  • jellyfish
  • leather
  • license plates
  • mass of tangled hair
  • monkeys
  • mutton birds
  • nails
  • nuts and bolts
  • nuts
  • oceanographer drift marker
  • old pants
  • oral contraceptive dispenser
  • overcoat
  • pair of shoes
  • paper
  • pelicans
  • pieces of coal
  • pig parts
  • pigs
  • plastic bags
  • rags
  • raincoat
  • rats
  • roll of chicken wire
  • roll of tar paper
  • rubber tire
  • sack of coal
  • seagull
  • seeds
  • small barrels
  • spaniel with collar
  • steak bones
  • tin cans
  • tom-tom
  • tools
  • tunicates
  • 2-pound (1-kilogram) can of peas
  • 2-pound (1-kilogram) coil of copper wire

Friday, April 29, 2011

The Tiger Shark

Galeocerdo cuvier

Tiger Shark teeth.
The Tiger Shark,  is one of the world's most dangerous sharks. Named for their stripes that fade as the animal gets older, the tiger shark is also known as the "garbage can of the sea". This name comes from the tiger shark's tendency to eat anything and everything that crosses their path. Just to name a few items found in tiger shark stomachs: a tom-tom, a chicken coop, license plates, drums, a goat, a suit of armour. In addition to garbage, tiger sharks eat dolphins, seals, seabirds, marine turtles, sea snakes, fish, sharks, rays, crabs, spiny lobsters, horseshoe crabs, octopus, squid, marine snails, and jellyfish. Their heavily serrated teeth have an indentation which makes the tooth look crooked. This unique tooth shape combined with a large bite force allows for the tiger shark to break the rock hard shell of marine turtles. Tiger Sharks are active at night and enter shallow reefs and lagoons after dusk to feed. The largest tiger shark ever recorded was 18 feet, but there have been some unconfirmed reports of tiger sharks longer than 30 feet! The females mature at 8 years, at 8 to 11.5 ft. Males mature at 7 years, at 7.5 to 10 ft. They are ovoviviparous (the females carry eggs that hatch in the womb, but are not attached by an umbilical cord to the mother) and their gestation period is 13-16 months. They can give birth to anywhere from 10 to 82 pups! However, as with all sharks, they do not care for their children.

note: I do not own any of these pictures.

Sunday, April 17, 2011

The Great White Shark

A Great White Shark off the coast of New Zealand
A gaping White Shark 
Of all shark species, Carcharodon carcharias is perhaps the best known and least understood. The white shark is a member of the Mackerel shark family whose members are "point endothermic". This means that they are not truly warm-blooded, but the movement of their muscles warms their blood. Now known more often as the white shark than the Great White Shark, these massive creatures can weigh from 1,500 to 4,500 pounds. Females become mature at the age of 14-16 years old, at 15-16 ft. Males mature at 9-10 years, at 11.5-12 ft. At birth they are 3-5 ft. long. Their gestation period is thought to be 18 months. White sharks are believed to be opportunistic feeders, but here are some of the items they are known to feed on: sharks (though they are not cannibalistic, they do eat smaller shark species), rays, fish, seals, sea lions, dolphins, squid, sea birds, marine turtles, crabs, snails, and whale carrion. Sadly, these beautiful and majestic creatures are vulnerable of becoming extinct. Over fishing combined with slow reproduction rates means dropping shark numbers, not just in Great Whites, but in all shark species.

note: I do not own any of these pictures.