Sharks are cartilaginous fish belonging to the class Elasmobranchii, and there are over 400 species of them in the world. According to the fossil records dating back 400 million years, sharks have outlived many forms of lives, dinosaurs included, and new species remain discovered every year.
Sharks are majestic and top predators who are crucial for the natural order of marine ecosystems. They are the ones that are threatened most by overfishing and piracy. Sharks have been around for many years, which means that there’s a lot to learn about them as the most feared predators of the ocean.
Sharks have for long been on the receiving end of bad press, especially in recent years, but they are fascinating creatures with unique behaviors, traits, and qualities.
Unlike most species of animals, which go extinct after millions of years, sharks keep being an irreplaceable and dependable source for coastal communities for centuries. Restoration of sharks in the oceans, which have now been significantly degraded, is crucial in improving oceans’ resilience to changes.
Sharks and rays are very enigmatic creatures that have been misunderstood by many people for years and are very important for the planet’s health.
There are hundreds of species of sharks classified into eight very distinct orders. These orders give sharks their unique distinguishing characteristics, which helps understand the different types of sharks that are different from other fish species.
Sharks come in all sizes and shapes, and they can be found in every ocean worldwide. They have such defining characteristics as rigid fins, an exoskeleton made of cartilage rather than bone, five to seven gills, placoid scales, and enhanced senses.
These creatures have a unique ability of electroreception, which helps them sense electric fields underwater.
What Affects the Shark Population In The World?
The population of sharks around the world is in constant and rapid decline, as sharks grow relatively slowly, and it takes years for them to mature. Sharks have a relatively low production of offspring, which is what makes sharks vulnerable to over-exploitation.
Sharks are threatened by illegal fishing for fins and overfishing, which dramatically affects their population in the world. There is no proper form of essential management, monitoring, or control of fisheries to combat pirate fishing of sharks.
The shark population is precarious and unsustainable, especially with the demand for shark fin. This precious commodity is traded and is often used to make a very expensive Asian soup, posing a great danger to most shark species.
In an estimate, about 100 million sharks are killed every year for their fins, which is a practice that affects most of the shark species.
Defining Features of Sharks
Sharks have several rows of teeth on their jaw lining, and they are constantly shedding and replacing these teeth with new ones. A shark loses and replaces thousands of teeth in one lifetime, but not all shark teeth are the same.
Depending on the fish’s eating habits, some have pointed teeth, others still teeth like the filter-feeding sharks, others razor-sharp teeth to bite chunks off prey, and others such as shellfish eating sharks have flatter teeth to break shells.
Sharks have an array of gill slits, which is another distinctive and defining feature. Bony fishes usually have a single gill slit on either side of the body, but most sharks have five slits on both sides, open individually, with some six or seven.
Sharks have for millions of years been known as some of the speediest swimmers found in the ocean. They have some distinctive and unique adaptations which help in this effect.
Sharks have a unique skin, comprised of millions of v-shaped, small, placoid scales called dermal denticles. These rows of denticles are smooth on one side, and in the opposite direction, they have a sandpaper feel.
They resemble teeth, which makes it easy and possible for water to flow through smoothly past the shark’s skin. The structure of the skin helps in minimizing friction and increasing the shark’s swimming efficiency.
Most of the shark species known for their speed have a slim, torpedo-shaped head, which helps them achieve quick bursts to help them fly into the air. Sharks can also gain some extra speed by swinging their tails back and forth to stiffen them.
Unlike bony fish, sharks lack swim bladders, which help fish in maintaining their position in the column of water. A swim bladder helps bony fish stay neutrally buoyant in water, and as sharks lack this, they have very large livers filled with oil and a cartilage half as dense as bone instead.
Sharks have a very lightweight skeleton, which allows them to put more energy into swimming. The light exoskeleton gives them a dynamic lift, which helps them maintain a balance and their place in the water.
What Are the Different Types Of Sharks?
Over 450 known living species of sharks have been taxonomically grouped into 14 to 30 families for ease of identification. The bigger species of sharks pose a threat to humans. Even with the many species available, the population of sharks is still threatened by commercial fishing and overfishing of certain shark species.
Sharks vary in sizes and shapes, but their anatomy is the same across all species and types. As a member of the elasmobranchs subclass, sharks’ exoskeletons are made of cartilage, which is a hard but flexible material and a defining feature of most elasmobranchs. Cartilage is lighter compared to bone, which allows these creatures to stay afloat and swim for long distances with minimum energy.
Different shark types have different and unique teeth, which scientists can use to identify bite marks on prey. A shark’s tooth type helps determine what the shark eats, which can help in classification. Some sharks have triangular and serrated teeth others have still tiny teeth for filtering out microscopic organisms out of the water.
Overfishing is another issue affecting different types of sharks and their population in the world today. The rising demand for sharks and their fins has brought about a severe threat to the population of different types of sharks.
The general lack of management of shark fisheries doesn’t help the situation. Other shark species like porbeagle and spiny dogfish are poached for their meat primarily.
Every year, millions of sharks are fished to keep up the consistent demand for shark meat and fins, bringing about the classification of endangered and vulnerable sharks. Sharks are commonly wanted for the rising demand for their meat fins, liver oil, cartilage, and leather.
The biggest threat of sharks is overfishing as open ocean long lines use thousands of hooks to catch great volumes of sharks. A vast population of sharks is found in oceans.
Still, there is some refuge from pelagic species and industrial fishes like the Oceanic Whitetip, which has an inability to reproduce quickly. A large percentage of these pelagic shark species face a threat of extinction.
Just like other shark species, Reef sharks also face a threat of overfishing, especially the larger Reef sharks. These added to reef damage and damage of other key habitats affect Reef sharks’ population in the world.
When mangroves are cleared, reef sharks are greatly affected, especially because their young use these habitats as nursery grounds. Other factors like climate change and loss of coral reefs as a result of sedimentation greatly minimize prey for sharks.
Bullhead Shark (Heterodontiformes)
These sharks are mostly known as bullhead sharks. They can be found in rocky reef surroundings in Indian or Pacific oceans. Bullhead sharks are small in size, with the largest from the heterodontiformes order being five feet long.
These sharks have short snouts and a large brow over their eyes, and an appearance that is considered cute. Bullhead sharks have small spiracles for breathing, a groove running from their mouths to their nostrils, and a small spine on either dorsal fin.
Their teeth are peg-like, which allows them to hunt prey with hard shells. Generally, bullhead sharks are considered clumsy, but they are definitely not the most sharks’ regular sleek killing machines. Some notable species of these sharks are Horn sharks, Zebra bullhead sharks, Galapagos bullhead sharks, and Port Jackson sharks.
Mackerel shark (Lamniformes)
This order of sharks has some of the most popular and notorious shark species in the world. Lamniformes are popularly known as mackerel sharks, and they come in a variety of body types and species.
The body types of Lamniformes range from giant filter-feeding sharks to sleek, predatory sharks. Lamniformes comprise a wide variety of species, and characteristically, they are considered typical sharks with two dorsal fins, five gills, and an anal fin.
Most members of the Lamniformes order are apex predators in their natural habitats except the filter-feeding ones. They range in size, and their body temperatures are warmer compared to the surrounding water temperatures.
They have varied diets, shapes, and sizes, with some eating other microorganisms and others chowing down on Tuna and Sea lions. Some of the most notable species of Lamniformes are Great white sharks, Basking sharks, Sand Tiger sharks, Thresher sharks, and Longfin Mako sharks.
These sharks are popular for their impeccable sense of smell and the many rows of teeth. Lamniformes, like the great white sharks, are often found in cold waters of the Atlantic and Pacific oceans, where they stay deep and partial to the open ocean. However, they can survive in warm waters, but they don’t go to shores to bear young ones.
Pristiophoriformes are commonly called Saw sharks, and they are mostly found in tropical and temperate oceans. Saw sharks are a small type of sharks characterized by rostrums or saw-like snouts.
Their snouts are edged for use in splashing their prey, and their teeth vary in size depending on the different species. These sharks are ovoviviparous, meaning that they give birth to live young ones.
They have long barbels, which are mustache-like and small, but their most notable feature is the snout. Some of the most common species of Pristiophoriformes are such as African dwarf saw sharks, Japanese saw sharks, the Bahamas saw sharks, and Sixgill saw sharks.
Ground shark (Carcharhiniformes)
This is the largest order of sharks consisting of more than 270 species. The Carcharhiniformes sharks live in most marine ecology types, from brackish rivers to frigid open waters. Depending on their species, Carcharhiniformes can be as small as 18 inches or as long as 20 feet.
These sharks are characterized by a membrane over their eyes, five gills, an anal fin, and two dorsal fins. The nictating membrane covering their eyes offers protection from injury while allowing the shark to see. Carcharhiniformes have longer snouts, and they adapt to a variety of environments.
These sharks are such as Blue sharks, Tiger sharks, Hammerhead sharks, Bull sharks, and Oceanic whitetip sharks. Some Carcharhiniformes like the Bullshark are very hostile, and they eat young members of their own species.
In addition to this behavioral tendency, Bull sharks are both salt water and fresh water sharks. They are found off the African and American Coasts of the Indian and Atlantic oceans as well as in murky waters of lakes and rivers.
Dogfish Shark (Squaliformes)
The sharks in this order are of 126 various species, and they are mostly found in deep ocean waters close to the ocean floors. There is little knowledge about these sharks, given their remote living environment, and the species have a considerable variety of shapes and sizes.
These sharks have spines on either dorsal fin and five to seven-gill slits, just like heterodontiformes. Their most distinctive characteristic is their ability to glow in the dark or their bio-luminesce.
This adaptation is believed to help sharks identify members of the same species, lure prey, and avoid predators. The most popular species of
Squaliformes include Pacific sleeper sharks, Greenland sharks, Spiny dogfish sharks, Lantern sharks, and Sailfin rough sharks.
Cow and Frilled Sharks (Hexanshiformes)
The number of gills easily identifies Hexanshiformes. Most sharks have five gills, but this type has either six or seven-gill slits, and they are large, ranging from eight to sixteen feet long.
These sharks have only one dorsal fin, unlike other types with a set of two, and they are considered very primitive types of sharks. Hexanshiformes have thin eel-like bodies and are usually hard to track given their habitats.
They prefer living in the deep and cold waters of the Indian, Pacific, and Atlantic Oceans. One know notable characteristic of these sharks is they are ovoviviparous in nature: their eggs hatch inside the bodies of the females and are born alive. Scientists don’t know what these sharks feed on as they are not easily trackable.
Examples of Hexanshiformes are Cow sharks, Frilled sharks, Broadnose Sevengillsharks, and Bluntnose sixgill sharks.
Angel Shark (Squatiniformes)
Squatiniformes are often confused with Rays, and they are mostly known as Angel sharks. There are about 13 species of sharks in this order, all falling in the same family.
Their confusion with Skates and Rays is attributed to their flat body and large pectoral fins resembling wings hence their name angel sharks. Squatiniformes are found on ocean floors and sandy areas, just like Rays, where they hide and secretly ambush their prey.
Their characteristic features are horizontal, pelvic, and pectoral fins, no anal fin, and a five to seven feet length. You can easily tell these kinds of sharks apart from Rays and Skates by looking for their pectoral fins, which are attached to their torsos instead of their heads.
Angel sharks used to be one of the most abundant species in Northern Africa and Western Europe, although they can be found all over the world.
They linger on bottoms of water bodies due to their flat bodies where they stay buried in the mud and sand with just their eyes poking out. Angel sharks maintain this position for days as they wait for their prey.
Unfortunately, this type of shark has been driven almost to extinction by pirate fishing and overfishing, making them critically endangered species and their fishing illegalized. Angel sharks are easy to catch in fishing nets, which makes them one of the most endangered shark types.
Some popular examples of Squatiniformes are Pacific Angelsharks, Clouded Angelsharks, Sawback Angelsharks, Smooth back Angelsharks, and Ornate Angel sharks.
Carpet shark (Orectolobiformes)
This type of shark, also known as carpet sharks, comes in a variety of sizes. They range from the largest existing sharks to the most diminutive sharks, but the Orectolobiformes prefer living in warm waters despite the size difference.
There is a noticeable behavioral difference between different types of carpet sharks ranging from habitat to feeding behaviors. For instance, Whale sharks are considered pelagic as they live in open waters and mostly eat plankton, while Bamboo sharks feed on invertebrates and small fish, and they prefer living in coral reefs.
The most notable feature of Orectolobiformes is their mouths found on the front of their heads. These fish have spot barbels around their mouths, which function as whiskers to help them when preying. Another notable feature of these sharks is their long caudal fin, which is the same length as the body for many species.
Carpet sharks have eye-catching patterns hence their name, with some of the most popular species being Zebra sharks, Whale sharks, Necklaces, carpet sharks, and Ornate wobbegongs.
There are different types and hundreds of shark species varying in color, shapes, sizes, habitats, and behavioral characteristics. Open ocean species feed near water surfaces and are most targeted by fishermen.
The fertilization of sharks is internal, with most species hatching their young from eggs. Other species nurture their young in the uterus just like humans using a placental attachment, some lay eggs while other species consume their siblings even before birth.
Generally, large sharks have fewer natural predators than small juvenile sharks, which are preyed upon by large fish and birds. Sharks generally have slow growth and low reproduction rate, and the rising threat of overfishing is greatly endangering their populations and ecosystems in the world.