Class:  Chrondrichthyes

Sub Class: Elasmobranchii - Sharks and Rays

CLICK HERE FOR SHARK AND RAY FIELD GUIDE


Evidence suggests that Sharks have lived in our seas for around 430 million years, placing them on earth before the dinosaur. Since this time they have changed very little.

Different species live throughout the worlds oceans, mostly in salt water although the Bull Shark will happily inhabit fresh water, there are approximately 370 named species of shark. They come in a variety of shapes and sizes but all have the characteristic streamlined body allowing them to cut through the water with ease, most sharks never sleep, instead they have rest and active periods.

Propulsion is from the tail (caudal fin), dorsal and pelvic fins act as stabilizers, pectoral fins lift the shark as it swims, illustrated left.

Located around the head are jelly like pores called Ampullae, these are electro receptive organs used to detect the presence of any living creature, useful as every living thing produces an electric field. They are formidable hunters with six senses, vision, taste, hearing, vibration, smell and electro perception.

The colouration of open water species is known as "countershading" their dorsal side (top) is dark, when seen from above they blend with the colour of the deep ocean, their ventral side (under) is light - when seen from below they blend with sunlit surface waters.

Unlike bony fish a sharks skeleton is made from calcium rich cartilage, this is more flexible than bone allowing sharks to turn tighter than a fish of the same size, although fish have more moving parts to their skeleton making them more agile.

Their rough skin is covered with little tooth-like scales called denticles and their bodies are held together mainly by muscle and tough skin.

Sharks do not have a swim bladder for buoyancy, cartilage is lighter than bone which helps them float, also aiding buoyancy is a large liver filled with oil which is less dense than water, many species however must continue to swim otherwise they would sink.

They have five to seven  gill slits on each side of their head, bony fish have just one.

In order to breath many sharks must swim so that oxygen rich water is pushed through these gills, some sharks however, such as White Tip Sharks have spiracles, leading to the respiratory system, these force water across their gills allowing for stationary rest.

The shape of their teeth depend on the food they eat.  Most teeth are triangular in shape, some are smooth while others have zigzag edges. Different shapes are used for seizing prey, cutting or crushing.  They are presented in rows, the first being the ones in use with replacements behind, it is very common for teeth to fall out when feeding. Whale Sharks, the largest of all fish have very small teeth as they are filter feeders, living on small fish, squid, krill and crustaceans.

They eat about 2% of their body weight per day, slightly less than humans, although some can go for a year without eating, surviving on the oil stored in their liver.



Reproduction
Females are generally larger and a lot rounder than males, Males have two claspers, which are two sex organs that protrude from the pelvic fins located on the underside.

Why they have two is still unknown as only one is used to mate!

During copulation the male bites the back of the females head, for this reason females have thick skin in this area for protection.

Females have an oviduct and to mate they swim parallel to one another.

Sharks mature at a similar rate to humans but the females pregnancy can in some species last more than one year, some give birth to live young and some lay eggs.



Sharks Need Friends

Although Sharks are some of the oldest and most successful vertebrates on the earth, many now are becoming increasingly threatened.

They are big business, as demand grows for shark products more and more are targeted.

Over 150 million are killed each year and because their reproduction rates are low, they have long gestation periods and do not mature until about the age of 20 years, the millions that are killed are not being replaced. 

They play an irreplaceable role to balance ocean ecosystems, for more information on Shark Awareness please visit our Fish R Friends Link (coming soon).




Order: Orectolobiformes - Carpet Sharks

Carpet Sharks are generally bottom dwellers (with the exception of the Whale Shark) living in warm tropical seas. They can all breath whilst stationary, they have two dorsal fins and 5 gill slits.
 
Family: Rhincodontidae
Species: Rhincodon typus  - Whale Shark

Growing up to 18m in length this is the largest of Sharks, in fact it is the largest fish in the ocean. Unlike most other sharks, their mouth is located to the front of the head in order to filter feed krill, plankton, small fish and squid.

Primarily pelagic but seasonal sightings are common around certain reefs. Mainly solitary but sometimes observed in small groups, they swim swaying their entire body.

They give birth to live young around 2ft long and do not reach sexual maturity until the age of about 30 years old, some research suggests that if Man were to leave them in peace they could live to between 100 and 150 years old.

There has been a noticeable lack of Whale Shark sightings in the Tunku Abdul Rahman Park this season, please visit our News and Events page to see the post.
 




Family: Stegostomatidae
Stegostoma fasciatum - Zebra Shark

Less common than the White Tip but often sighted by divers on coral reefs.

Growing up to 3.5m in length they are born with stripes, hence the name but later develop a spot like pattern on the upper body surface. They lay dark coloured eggs that anchor to the sea bed, they are mainly nocturnal hunters feeding on crustaceans, shell fish and small fish.

Distribution, Tropical West Pacific and Indian Ocean with a depth range of 5 - 75m.






Family: Hemiscylliidae - Bamboo Sharks
Chiloscyllium punctatum - Banded Cat Shark, Brownbanded Bamboo Shark

Found in low light areas, often hiding beneath overhangs and ledges. Feeding on invertebrates and crustaceans. Juveniles have more distinct and darker bands and spots than adults. Image above shows these bands fading which would indicate the animal is reaching adulthood. Interestingly its said that this species can survive in excess of 10 hours out of water.

Distribution, Indo - Pacific. East coast of Indian Ocean, to Northern Australian, Japan and eastern Philippines with a depth range of 0 - 85m.






 
Order: Carcharhiniformes - Ground Sharks

Family: Carcharhinidae
Triaenodon obesus - White Tip Reef Shark

Reaching up to 1.5m in length and preferring coastal reef habitats from the shallows to 60m depths. This species spends most of the day resting in caves or under overhangs and feeds at night.

They reach sexual maturity at the age of about 5years old and they are viviparpous (give birth to live young) in litters of 1-5 after a 5 month pregnancy.

Their distribution is Red Sea, Indian Ocean and Central Pacific.






 
Family: Carcharhinidae
Species: Carcharhinus amblyrhynchos - Grey Reef Shark

Known to demonstrate assertive territorial behaviour and therefore must be notably respected. Usually they will warn off whatever they see as a threat by arching their backs and pointing their pectoral fins downwards.

They are found on outer reefs at depths of 15 - 250m. and sometimes are observed schooling in numbers. Growing to 2.5m they are a robust looking shark with a much larger girth than the White Tip Shark, notice the darker shading that edges their caudal and pectoral fins.

Their reproduction is viviparous with 1-6 pups in a littler after a 12 month gestation period. They mature at approx 7 years of age and live for about 25 years. They can be active during the day and night usually preferring to hunt at night but they must continue to swim in order to breath.