Shark
Sharks (suborder Odontoceti) are a large group of predatory cartilaginous fishes, including the largest fish species in the world, the whale shark. As well as the familiar fierce types of shark, the family also includes various dogfish and the bottom-living wobbegong.
A shark's most notable characteristics include a prominent dorsal fin, fully replaceable teeth (with the exception of the whale and basking sharks) and a cartilaginous skeleton.
Species of shark
- Whale shark.
- Basking shark.
- Great white shark.
- Mako.
- Porbeagle.
- Tope.
- Whitetip reef shark.
- Oceanic whitetip.
- Blue shark.
- Tiger shark.
- Greenland shark.
- Megamouth shark.
- Nurse shark.
- Hammerhead shark.
- Bull shark.
- Ganges shark.
- Leopard shark.
- Wobbegong.
- Port Jackson shark.
- Cookie-cutter shark.
- Goblin shark.
- Dogfish.
and many others.
Behavior
Many species of sharks give birth to a few dozen live young, others lay a similarly small number of eggs; these are often washed ashore and are known as mermaid's purses.
Sharks are reputed to be able to detect minute amounts of blood in water, and to be able to follow blood trails for miles. In fact, although sharks can detect blood at concentrations of as little as a few parts per billion, a very considerable quantity must be spilt before it is detectable amongst billions of gallons of seawater. Sharks actually use sounds and vibrations to locate most of their prey.
Classification
Sharks belong to the holobaramin that also includes skates and rays.
Environmental Concerns
Worldwide, sharks suffer threats from over-fishing, mercury poisoning, ocean acidification, and habitat disruption. [1]. Many individual shark species are currently threatened or endangered, often because of human activities such as careless fishing practices and coal fired plants dumping tones of toxic mercury into the oceans.
