HomeSea LifeMarineVertebrates › Sharks

Information about Sharks

[Phylum: Chordata] [Class: Chondrichthyes] [Subfamily: Elasmobranchii] [Clade: Selachimorpha]

According to the IFAW, over 500 different shark species are currently swimming in the oceans and we can separate them into ten individual orders.

This section contains fun facts and interesting information about shark phylum, acknowledged as being the biggest predator among all fishes.

Shark Phylum and Class Explained in Detail

There are some dumb fish names in existence. But, the field of science used to classify and name shark species is "taxonomy".

As such, taxonomic classification is the bedrock for shark conservation groups and in wildlife conservation.

Plus, understanding shark characteristics and behaviour is easier when there is a worldwide naming system to follow.

It's a format that marine biologists use to track how species are related and how they fit into aquatic ecosystems.

As a consequence, the methodology invented by Swedish scientist 'Carl Linneaus' in the 1600s, removes many of the previous complexities used when they named and standardised plant and animal species.

Taxonomy of a Shark

Kingdom

The grouping of all organisms consists of two major categories, animals (Kingdom Animalia) and plants (Kingdom Plantae). All shark species are animals, so they belong with the Kingdom Animalia.

Phylum

The first division of the two Kingdoms creates several smaller groupings that share similar characteristics. Sharks have a spinal cord, a notochord, and a backbone (aka vertebrae), so they belong to the phylum Chordata and the subphylum Vertebrata.

Class

Scientists classify marine vertebrates into one of the common animal groups (e.g. amphibians, birds, mammals, fish, and reptiles).

All fishes that have a skeleton made of cartilage, including sharks, belong to the Class Chondrichthyes. But, further divisions create two more subclasses, Elasmobranchii (e.g. rays, skates, and sharks) and Holocephali, soft-bodied Chimaera (e.g. ghost sharks, rat fish, and spookfish).

Order

The subclass Elasmobranchii divides into two (2) superorders for extra identification purposes. Today, we only use ten orders to identify modern sharks:

Family

Species that have close relations with other similar members of the animal Kingdom are grouped in families. So, a typical example is the Family Primates that includes apes, monkeys, and human beings.

A good example in fish is mackerel sharks. The seven families in the order Lamniformes contain the basking shark (Cetorhinidae), but there is only one (1) species. Whereas, the thresher shark (Alopiiidae), with its scythe-shaped tail, has three (3) different species.

Genus

In marine biology terminology, genus refers to the first word of the scientific name for each species. Hence, two or more species sharing the same genus shows they have some close relationship with each other.

Species

Groups of plants and animals that have the capability of producing fertile offspring, such as whale sharks with the scientific name Carcharodon carcharias, belong with that particular name for the species.

A to Z List of Shark Species

Angel Sharks

Several biological differences and unique predatory habits distinguish the common angel shark (Squatina squatina) from most other sharks.

This guide contains fun facts and information about angelsharks, including where they live, what they eat, and why some species are critically endangered.


Blacktip Reef Shark


Bull Shark

In fact, the bull shark is a marine animal that is also found in brackish waters - such as the Amazon River - thousands of miles from the sea.


Caribbean Reef Shark


Carpet Shark


Dusky Shark


Epaulette Shark


Galapagos Shark


Great White Shark


Hammerhead Shark

Compared to the other species of sharks, one of the genus is instantly recognisable by the unconventional shape of its head - shaped like a hammer!

This guide contains fun and interesting facts about hammerhead sharks (Sphyrnidae), including where you can find them, what they eat, and how they reproduce.


Horn Sharks

Some Heterodontus francisci species actually have horns that contain venom. But, the horn shark is mostly a harmless and solitary creature that hunts at night.

The horn shark facts and information section explains where Heterodontidae live, how their behaviour links with bullhead sharks, what they eat, and how they reproduce.


Indonesian Houndshark


Japanese Sawshark


Kitefin Shark


Leopard Shark

A leopard shark is instantly recognised by its leopard-like spots. The shark's yellow-brown skin tone is covered with dark brown spots.


Milk Shark


Nervous Shark


Nurse Shark

Despite being generally harmless to humans, one of the large bottom-dwelling predatory sharks has a wide curved mouth and makes a sucking sound when it searches for food in the sand.

Check out a segment that contains fun and interesting facts about nurse sharks (Ginglymostoma cirratum), such as what they eat, where they live, and how they reproduce.


Ocellate Topeshark


Pyjama Shark


Quagga Catshark


Shortfin Mako


Tiger Shark


Whale Shark

Whale sharks are unmistakably the largest living fish in the animal kingdom. In fact, individual species can weigh 20 metric tons and they can grow up to 18 metres long (60 feet).

This guide contains fun and interesting facts about whale shark species (Rhincodon typus), including where they still exist, what they eat, and how they reproduce.


Whitetip Reef Shark

It's fair to say the most distinguishing characteristics of the genus Triaenodon obesus are the grey slender body and the white-tipped dorsal and caudal fins.

Check out these fun and interesting facts about whitetip reef sharks, including where they still exist, what they eat, and how they reproduce.


Zebra Shark


100 Interesting Facts about Sharks

Habitat and Geographical Range

Around five hundred different shark species are still in existence today. The majority prefer to live in warm water environments, such as whale sharks.

Whereas, others thrive much better in cooler water, such as the great white shark, even at depths of 2,000 metres.

Then there are some species of shark, particularly the bull shark (Carcharhinus leucas) that are capable of living in saltwater and freshwater environments.

Whitetip Reef SharkIn general, every shark species will live in one of the following marine habitats:

  • Coral reef
  • Deep ocean
  • Estuary
  • Pelagic zone (open ocean)
  • Sandy plain

Only a few species actually fulfill their perceived role of being a solitary hunter. But in fact, most sharks live sedentary lifestyles and socialise in large schools during the mating season.

They respond to close approaches and high threat levels (e.g. when freediving with sharks) using a display of exaggerated thrashing and swim movements.

It is not unusual for pelagic sharks to roam the oceans and cover more than 1,000 miles each year. Recent reviews suggest their complex migratory patterns are similar to those in birds.

Pro Tip: Researchers and shark conservationists often use man made artificial reefs to study how nature restores itself and how new coral formations grow on the structures.

Behaviour and Characteristics

A shark is a fish that we can generally characterise using one of three groupings. The first characteristic is its cartilaginous skeleton, followed by the number of gill slits on each side of its head, and thirdly whether it has pectoral fins fused to its head.

In a process spanning thousands of years, sharks have evolved into the ultimate predators and rank among the most powerful creatures in the Blue Planet (e.g. seas and oceans).

Despite that interesting fact, or because of it, the shark phylum has a critical role to perform in oceanic and freshwater ecosystems.

For example:

Regulating the populations of other large predatory fish, such as groupers, is vital for the long term survival of coral reef habitats and sea grass.

Therefore, the underwater world needs an abundance of herbivores (plant eaters) to feed on macroalgae to stop it overpowering the reef systems.

Size and Description

Sharks are cold-blooded animals (ectothermic) with a skeleton made of cartilage and gills for respiration in water.

Excluding two species of shark, sixgill sharks and the broadnose sevengill shark, they all have five external gill slits.

The strength and flexibility of dermal denticle covering improves a shark's fusiform body shape, which also helps it resist parasitic infection.

Here's the thing:

The dwarf lantern shark, midwater shark, the dogfish, and the pygmy ribbontail catshark, are the smallest measuring less than twenty (20) centimetres in length.

Yet, the colossal whale shark is one of the biggest, measuring in at a gigantic twelve (12) metres long and weighing in excess of twenty (20) tons.

Diet and Eating Habits

Shark teeth are not anchored in the jaw, like bony vertebrate fishes, and they are able to replace the ones that fall out. In fact, some Carcharhiniformes can shed around 35,000 teeth in a single lifetime.

Most extant sharks are carnivores, which means they eat large marine animals (especially seals), squids, and sea turtles.

The rest are planktivores (e.g. basking sharks, megamouth sharks) that feed on microscopic plankton and zooplankton.

Interesting Fact: Like most cold-blooded animals, sharks have a slow metabolism and they don't eat big quantities of food (usually less than 10% of its total body weight per week).

Lifespan and Reproduction

The majority of shark species can live up to thirty (30) years of age. But, they have a very low reproductive rate.

In general, the male has external claspers on the underside of the body in front of the caudal fin. Like most vertebrate sea animals, the females tend to be larger than the males.

After mating, the exact period for gestation will depend on the different shark species. But, some females are oviparous (lay eggs), viviparous (give birth to living young), and others are ovoviviparous (eggs hatch inside the parent's body).

Threats and Predators

Contrary to popular belief, sharks are not the deadliest animals to humans, not even close! Yes... There are about thirty (30) shark species that do attack people. But, it usually happens as an accident (e.g. mistaken as food) or while defending their territory.

Even so, the migratory, live-bearing requiem sharks (of the family Carcharhinidae) are involved in many of the attacks on humans. Requiem shark species include:

  • Blacknose shark
  • Requiem Shark Species: Bull SharkBlacktip shark
  • Blue shark
  • Bull shark
  • Copper shark
  • Dusky shark
  • Grey reef shark
  • Lemon shark
  • Silky shark
  • Spinner shark
  • Oceanic whitetip shark
  • Whitetip reef shark.

Recent studies suggest that about 50% of all shark species are either threatened, or near threatened, with extinction.

So, what is the biggest killer of sharks? In fact, there are many reasons for the present-day decline in most species of shark, including:

  • Commercial fisheries
  • Garbage pollution
  • Human behaviour
  • Loss of habitat
  • Overfishing
  • Slow reproduction rates

It gets even worse! The number of oceanic pelagic sharks has dropped by around 71% during the last fifty years. Official estimates of the sharks killed each year is close to 300 million (over 100 million sharks killed annually in commercial fisheries).

According to the IUCN Red List of Threatened Species, a recent assessment (February 2024) for the whale shark (Rhincodon typus) lists the species as decreasing in numbers and "Largely Depleted" (LD).

The list of endangered sharks includes the basking shark, goblin shark, hammerhead shark, and the tiger shark.

Despite this, many shark conservation groups consider their survival as being unstable and vulnerable, with some shark species being reported as "threatened with extinction".

Sharks Information and Resource Help Guides

Note: The short video [2:25 seconds] presented by "Deep Marine Scenes" contains incredible footage of the biggest fish living in the oceans today - the whale shark (Rhincodon typus).

Divers also enjoyed reading about...