Introduction

The legendary great white shark is a cartilaginous fish that has caused fear and admiration for many years. It is considered one of the biggest predators of the oceans and the fiercest, but there is more imagination than truth in this sentence. His reputation as a “man-eater” is also far from reality.

The white shark is a member of the class Chondrichthyes, the subclass Elasmobranchii, the order Lamniformes, the family Lamnidae and the genus Carcharodon.

DESCRIPTION

The body of the white shark is robust and fusiform, about 4-7 meters in length but the average is 6 meters. Its weight is between 3,000 and 3,400 kilograms. Adult females reach dimensions greater than males, which are usually 2 meters smaller.

Their sense of smell is very sensitive, which facilitates the detection of prey at a great distance.

It has a narrow pointed snout, two pectoral fins and a first dorsal fin with a triangle shape. The caudal fin is crescent-shaped, and its upper and lower lobe are long and of very similar size, almost symmetrical. The mouth measures 0.9 to 1.2 meters wide; Is provided with several rows of sharp and serrated triangular teeth, that the shark changes several times throughout his life. It has small onyx eyes and nostrils towards the end of the snout.

It exhibits discoloration of the body, because while the back is gray or blue, the lower area is lighter. This characteristic gives an advantage when hunting because preys do not notice the figure of the shark, which is confused with the bottom of the ocean.

Their sense of smell is very sensitive, which facilitates the detection of prey at a great distance, and together with the Lorenzini ampoules which detect electric fields of moving animals make them efficient predators.

Facts on video

DISTRIBUTION AND HABITAT.

The distribution area of the great white shark is very extended; It ranges from the latitudes 60 ° north to 60 ° south and can be found in tropical coastal waters as well as temperate and even cold. In general, the temperature of the water that inhabits oscillates between 12 ° and 24 ° Celsius.

It is commonly found on the coasts of North America from Newfoundland to southern Mexico in the Atlantic Ocean and from Alaska to southern Mexico in the Pacific. Outside of the American continent, the great white shark dwells mainly the waters of South Africa, the Mediterranean Sea, Japan, and Oceania. There is a substantial population in the Dyer Island in South Africa, and that is why there is a common place for research about their life.

Their habitats include coasts and continental and insular platforms whose waters do not surpass 1,875 meters of depth. In the open ocean, it inhabits to depths of up to 1,200 meters. It is an epipelagic shark that has been seen close to the shore on many occasions, but it is not an eminently coastal species.

Great White Shark – Carcharodon carcharias.

FEEDING

The diet of this shark species is, of course, carnivorous. However, it does not usually feed on large species, but on smaller animals such as squids, rays, and other fish. Adult individuals also include other sharks, seals, sea lions, dolphins and whale corpses. They sometimes catch turtles and seabirds to feed on them. They have a clear preference for fat-rich prey.

They have different hunting strategies depending on the target victim and the size of the species. The most usual approach is that, once they detect by electroreception their possible food, they locate below and then stealthily swim vertically. Once closer, they inflict a deadly bite and wait for the animal to bleed and die and then eat it. If the prey survives that, they try to hold it with their lower teeth while the upper tear the tissues. The most common forms to die of their preys are decapitation, mutilation, and bleeding.

BEHAVIOR

The great white shark is a fish mostly solitary although it can reunite with others of its same species. He has been seen a few times accompanied by a female or a male and even in small groups. In their groups, it is likely that there is hierarchical dominance, and the females are in the lead, but among all, large individuals dominate the small ones, and the residents of the group for a long time dominate the newcomers.

This shark is active both day and night. Interestingly, they jump out of the water sometimes to look the surrounding and look for prey. They are not aggressive with their own species, but if they feel threatened, they may bite his antagonist as a warning.

Most people expressly fear the great white shark and consider it a man-eater predator. Definitively, it is a powerful, aggressive and efficient predator, but it has no preference for humans. The attacks usually happen because of the shark confusion of a person with prey, and as a consequence, they give a “test bite,” but it is unlikely that it keeps eating once it finds that it is not its usual food.

REPRODUCTIVE HABITS

Males sexually mature about nine years old, but females mature between 14 and 16 years. This species is slow growing, late maturing and relatively long life.

Their reproduction is ovoviviparous. Bites on the flanks, backs and pectoral fins of females indicate that males exert “soft” aggression before and during mating. Males fertilize the eggs internally, inserting their claspers into the female oviduct so that eggs develop inside their body. Before birth, developed embryos presumably practice oophagy.

The gestation period lasts between 12 and 18 months, after which the female gives birth between 2 to 10 live offspring measuring more than 1 meter long. Female gives birth every 2 or 3 years.

THREATS AND CONSERVATION

The great white shark is at the top of the food chain, and except for killer whales, whales, and humans, it does not have predators. However, the Red List of the International Union for Conservation of Nature (IUCN) has classified it as a “Vulnerable” species, since overfishing and by-catch have led to a decrease in the number of individuals, as they have a low reproduction rate.

Some countries such as the United States, South Africa, Namibia, Malta and Australia protect the great white shark within their oceans, but it is still a feared and misunderstood fish. Therefore the conservation efforts do not have enough reach and impact.

Great White Shark Infographic!

(Click for expand)

Sources:

https://en.wikipedia.org/wiki/Great_white_shark

http://www.iucnredlist.org/details/3855/0

World of Animals Magazine. Issue 1. Imagine publishing.

World of Animals, Book of Predators. Imagine publishing. 2014

http://www.arkive.org/great-white-shark/carcharodon-carcharias/

http://sharkopedia.discovery.com/types-of-sharks/great-white-shark/#top-10-greatest-great-white-videos

BioExpedition Publishing © 2017.

Introduction to Hammerhead Shark

Even if you struggle to keep various species of sharks clear in your mind from the rest, this is one that you will easily remember. They have the unique shaped head that has made them such a fascinating to experts as well as to the general public. There is no other species of shark out there compared to the look of the Hammerhead Shark.

Hammerhead Shark Description

As mentioned, this species of shark has a head that is wide like the head of a hammer and then a long handle as it goes back to the rest of the body. This shape is actually appropriately called cephalofoil. This shape allows them to have excellent sensory receptors, to easily manipulate their prey, and for them to move around in the water with ease.

There are several subspecies of them, and they can dramatically vary in size. Some of them are only 3 feet long and others can grow to a size of up to 20 feet long. They can also vary a great deal in weight from 500 pounds up to 1,000 pounds. Both location and their food sources also influence the overall size of Hammerhead Sharks.

They feature a light gray color but if you pay close attention to them you will also see a green-colored tint as well. They have a white belly so that they can easily sneak up on their prey in the water. It is believed that they have better vision than other species of sharks due to the shape of the head and location of their eyes. They have a 360-degree vision so that they can see above and below them in the water at the same time.

They also rely on their electro receptor sensors so that they can feel vibrations and movements in the water. This makes it very simple for them to find prey even if it is barely moving in the water. Their mouths seem to be very small in proportion to their heads.

Hammerhead Shark Distribution

Hammerhead Sharks are found in many bodies of water around the world that are warm. They tend to live the most often through the continental shelves and the coastlines. Large numbers of them have been identified around Cocos Island close to Costa Rica and Molokai Island close to Hawaii. There are also many of them around both Eastern and Southern Africa.

During the summer months, the Hammerhead Shark migrates in very large numbers. They do so in order to find cooler waters where they will stay for the hotter period of the year. This is also when a great deal of the mating will occur and the migration allows them to find the greatest genetic pool to select from.

Hammerhead Shark Behavior

While most species of sharks are loners, the Hammerhead Sharks swim in schools during the daylight hours. These schools can have up to 100 members in them. At night time though they go to find food and they do that on their own. It is believed they spend time together during the day for protection but also that they enjoy socializing to some degree as well.

They aren’t known to attack humans, but they will do so if they are provoked and feel that they must do so in order for their own protection. This is especially true of females that are about to give birth. They aren’t territorial but they are instinctively going to do what they can to protect their needs.

Hammerhead Shark Feeding

Due to the ability to pick up movements in the water, they have very little trouble finding their prey. This combined with how well they blend into their surroundings and their ability to see and they are able to get food without wasting energy. They do eat large amounts of food every day and will consume all that they can find readily available. They are nocturnal which means they do their feeding at night.

Their diet consists of quite a variety of products. They include octopus, fish, squid, stingrays, crustaceans, and small sharks including baby Hammerhead Sharks. They tend to look for their food at the bottom of the water and they are very good predators. They use their head to pin down some prey such as stingrays. They consume their prey while it is in shock and unable to move. In some instances when food is very hard to find, the females have been known to consume their own offspring.

Many experts agree that this species so shark has the greatest advantage over other species due to the shape of the head and their eyesight. This could be a prime reason why they aren’t as at risk of dropping numbers as many other species.

Hammerhead Shark Reproduction

The rituals for mating may seem harsh from our point of view as the males fiercely bite the females. However, the females have very thick skin so they aren’t in pain from those bites. Still, many of the older females do have plenty of bite marks on their bodies from this process. Mating occurs annually for the Hammerhead Sharks and that helps them with increasing their numbers. Many other species of sharks reproduce at a much slower rate.

The females are in control over mating, and will often eventually give in to the advances of the male. However, she can decide to make him go away and wait for another male to mate with. These rituals can take hours though for the female to decide one way or the other.

The females give birth to live young, but they are left to take care of their own needs as soon as they are born. The litter can have from 12 to 15 pups in it but there is one species that can have up to 40 at a time. The young depend on the safety in numbers and swim as a group towards warm water. As they get older and larger they will start to separate.

Photo taken by Albert Kok

Tiger Shark – Galeocerdo cuvier

It is the only living species of the genus Galeocerdo and is also known as sea tiger, but it should not be confused with another species called leopard shark (Triakis semifasciata).

It is called “tiger” because of the dark vertical stripes on its body. It belongs to the order Carcharhiniformes, the Carcharhinidae family, and the genus Galeocerdo.

DESCRIPTION

This shark is one of the largest that inhabit the oceans only smaller than the whale shark (Rhincodon typus), the basking shark (Cetorhinus maximus) and the great white shark (Carcharodon carcharias). It reaches a maximum length of 7.5 meters but on average measures between 3 and 4.2 meters long while its weight ranges between 385 and 635 kilograms.

This shark has dark stripes on its skin similar to those of the land Tigers. However in the case of these sharks these bands fade as the individual gets old. The background color of their skin is bluish green or dark gray in the upper area and the ventral region is a yellowish color or white.

Its fusiform body has a narrow snout and a blunt nose; its tail has the upper lobe larger than the lower, and its mandible has serrated teeth important to break the hard shells of the clams and the sea turtles. It possesses an excellent sense of sight as well as smell.

DISTRIBUTION AND HABITAT

The tiger shark is found in tropical and subtropical waters around the world but mostly inhabit a range between the parallels 45 ° north and 32 ° south. Its presence ranges from the east coast of North America to the east coast of Brazil, including the Gulf of Mexico. The oceans of China, India, Africa, Japan and the Pacific Islands are also places where the tiger shark dwells.

It is a saltwater species and often approaches near the coasts with relatively shallow waters (2.5-145 meters deep). It inhabits seagrass, but also near atolls and even estuaries. It does not always stay in one place, so its habitat is changing.

FEEDING

The tiger shark diet is made up of fish, mollusks, crustaceans, sea turtles, seabirds and even mammals such as the dugong. It also consumes small sharks and the remains of dead whales or can even venture to attack the wounded and immobile cetaceans.

Tiger sharks have an enormous appetite and can eat almost anything they find in their path. That is why, if they run into non-edible objects or junk, they do not hesitate to eat them even without trying them first. In their stomachs trash, bags, and even license plates have been found.

They can camouflage with the environment and thus easily trap their prey. However, these sharks have one disadvantage: if their victim begins to flee, they recoil and do not pursue it since they do not engage in high-speed chases.

Although they have a reputation as a ferocious predator, they can survive several weeks without anything to eat.

BEHAVIOR

The tiger shark is a fish that prefers to live alone unless it is in the mating period. During that time it meets with other tiger sharks and groups establishing a social hierarchy based on their size, so larger individuals have access to prey before than the small ones. Once the elders are satisfied, the others can approach the carcasses of the unfortunate prey. Despite this dominating behavior, violence between members is almost nil.

These sharks perform their hunting activities during the nights, and because of their indiscriminate eating habits, they usually ingest non-edible objects and tastes human flesh, although attacks are rare.

They usually ingest non-edible objects and tastes human flesh.

REPRODUCTIVE HABITS

Both male and female have multiple sexual partners throughout their life, which is about 27 years in the wild. The female reaches sexual maturity around eight years old and the male at seven years old.

There is little information about the existence of a process of courtship. It is known that the female mates once every three years and reproduces through ovoviviparity. Fertilization occurs in different seasons in the southern hemisphere and the northern hemisphere. In the first, fertilization occurs between March and May and in the latter occurs between November and January.

The embryos develop inside the uterus and feed on the yolk sac and the secretions produced by the uterus. After 14-16 months the female gives birth to about 10-82 fully developed offspring which can survive without the help of the parents.

THREATS AND CONSERVATION

It has a status as a “Near Threatened” species on the IUCN Red List as a result of commercial and recreational overfishing. Like other species of sharks, their capture is highly demanded because some people believe that their fins have excellent nutritious, healing and aphrodisiac properties. Their skin, meat, and liver are also used for different human purposes.

At present, there are no specific conservation actions for the tiger shark but some marine life conservation organizations are pushing for stopping overfishing. Other initiatives insist on establishing a catch limit for fishers.

Sources:

https://en.wikipedia.org/wiki/Tiger_shark

http://www.iucnredlist.org/details/39378/0

http://www.arkive.org/tiger-shark/galeocerdo-cuvier/

http://sharkopedia.discovery.com/types-of-sharks/tiger-shark/

World of Animals Magazine. Issue 1. Imagine publishing.

BioExpedition Publishing © 2017.

The whale shark is a giant of the oceans: the dimensions of its body gives it the title of the largest fish in the world and therefore, also the biggest shark.

It is the only member of the genus Rhincodon. It belongs to the order Orectolobiformes and the family Rhincodontidae.

DESCRIPTION

This shark shares the name of the cetaceans because of its massive size, but it is a fish that can measure up to 20 meters long, although it has an average size between 9 and 12 meters long. It weighs over 12,500 kilograms. Its fusiform body is wide in the middle area and narrows in the tail and head that is wide and flat, and it has two small eyes on the front. Its mouth, located towards the end of the snout, can open about 1.5 meters. Inside there are 300-350 rows of teeth and ten pairs of useful pads to filter the food.

It has one pair of nostrils at the tip of the snout, lack of circumnarial grooves but it has rudimentary beards. It has five pairs of gill slits on each side of the head and spiracles behind the eyes. Like many pelagic sharks, it has one pair of dorsal fins (one larger than the other) and one pair of pectoral fins as well as a caudal fin.

The skin of the whale shark has a blue-gray coloration on the back and white in the belly. The upper area has light spots that form unique patterns in each shark.

DISTRIBUTION AND HABITAT

The extensive distribution of this pelagic species covers all the temperate and tropical seas of the world except the Mediterranean Sea. They inhabit waters in the latitudes between 30 ° north and 35 ° south in countries like Mexico, Belize, Ecuador, South Africa, Australia and the Philippines.

This shark inhabits both deep waters and shallow waters with temperatures between 21 ° and 30 ° C but tolerates water up to 3 ° C degrees in some cases. Their favorite habitats are coastal areas with abundant food.

Whale shark – Rhincodon typus.

FEEDING

Fortunately for many animal species (including humans), the natural food of the large whale shark is mainly plankton, although occasionally includes other small animals such as krill, jellyfishes, sardines, anchovies, mackerels, squids, and crabs, as long as they are small.

Their feeding method consists of suction and filtration; Is called “passive feeding” since there is little pumping and muscular activity in the gills while they eat. While swimming, the shark tends to keep its mouth open to access the food and suck it hard. Once inside, the whale shark closes its mouth, and the plankton gets trapped in its filtering organs, and at the same time, they expel the water through the gills. The reason for the presence of teeth is unknown because they do not use them for eating.

It can actively feed when it opens and closes its jaws to catch the food at any given time, and passively when it keeps its mouth open as it swims forward and the food gets inwards.

BEHAVIOR

It is one of the most docile sharks that exist and does not present any danger to humans. They even allow divers to have contact with them despite the scientists’ disapproval of this activity.

It is an intelligent animal who demonstrates the ability to learn. Captive sharks in aquariums exhibit changes in their behavior when humans come to feed them as they begin to swim in circles. Observations indicate that they sometimes perform a cough-like activity, presumably to clean their filter pads.

They usually swim unaccompanied by other sharks, but on certain occasions (feeding and mating) they travel long distances together. It is also possible that they modify their swimming patterns according to the environmental conditions.

Whale shark with remoras.

REPRODUCTIVE HABITS

Some scientists think that they have a polygamous mating system, but this is not confirmed. Except for some research, there is not much information about whale shark mating and reproduction and birth has never been observed.

They reproduce through ovoviviparity and females deliver live pups that reach a length between 40 and 60 centimeters. The number of offspring is not determined, but apparently, they are many because during the 90 s a female captured had about 300 fetuses inside. The pups are not born all at the same time; the female stores the sperm of a male and can develop new offspring after some time.

Males and females reach sexual maturity around 30 years old.

Facts on video

THREATS AND CONSERVATION

Despite their size, they are not free from predators in their natural habitat. Orcas, blue sharks, white sharks and blue marlin attack mainly young individuals who are still vulnerable because of their small size. On the other hand, humans considerably contribute to the status this shark has on the IUCN Red List: Vulnerable. Their meat is valued in Asia, and their fins are sold to elaborate soup with supposed medicinal and aphrodisiac properties.

The conservation efforts for this species are still incipients although some countries are already protecting them, for example, countries, like the Philippines, and Australia, regulate the activities related to whale sharks. Their capture is banned in that Asian country, and the Australian Department of Conservation is responsible for monitoring the tourist visits to the whale sharks.

 Whale Shark Infographic!

(Click for expand)

Sources:

http://www.iucnredlist.org/details/19488/0

http://www.arkive.org/whale-shark/rhincodon-typus/

https://en.wikipedia.org/wiki/Whale_shark

http://www.worldwildlife.org/species/whale-shark

http://animaldiversity.org/accounts/Rhincodon_typus/

BioExpedition Publishing © 2017.

The basking shark is the second largest shark in the world, only surpassed by the whale shark and, also, is one of the three planktivorous sharks. It is a “kind” shark for divers, despite its size and the impressive mouth that it possesses.

It belongs to the order Lamniformes, to the family Cetorhinidae and the genus Cetorhinus.

Description

The most impressive feature of the basking shark is its mouth, which opens up to 1 meter wide. It has a conical body covered with a layer of mucus, gray or brown skin on the back and white on the belly. Its dorsal and pectoral fins are so large that they can reach 2 meters each and its tail is crescent moon shaped.

It has a conical snout and large gills. Inside its mouth, this shark has several hook-shaped small teeth. Its liver is about 25 percent of its total body weight and is rich in squalene, a substance that helps the shark to float.

Its liver is about 25 percent of its total body weight.

Its weight ranges between 3,000 and 6,000 kilograms, and its length is around 6.7 and 8.8 meters.

Characteristics of the basking shark.
Basking shark – Cetorhinus maximus

Distribution and Habitat

The basking shark inhabits all oceans of the world, but it prefers the subpolar seas and in general cold and temperate waters of the continental shelves. It was recently discovered that it goes as far south as the equator and dwells into warmer waters.

Its habitat changes according to the food availability. In summer it goes to coastal areas to feed abundantly on copepods, but as soon as the winter begins, it migrates to cold water areas. Sometimes it gets close to the coast, and its great body is seen below the surface following concentrations of plankton near the surface.

Basking Shark – Cetorhinus maximus.

Feeding

Like the whale shark and the megamouth shark, the basking shark mainly feeds on plankton, so it is not a common predator. But unlike the other two species, it does not seem to actively seek for food or use the muscles of its head to suck water, instead, it usually swims with its mouth open and catches whatever it goes through. When the water passes through its gills, the spines of the gills rakers separate the plankton from the water. The shark closes the mouth and then pumps the water out through the gills.

The basking shark relies on the guidance of its large olfactory bulbs to detect food. It is a passive eater that can filter around 1,500-2,000 cubic meters of water per hour to obtain sufficient quantities of zooplankton, which also includes fish and small crustaceans, invertebrate animal larvae and fish eggs or larvae.

It feeds near the ocean surface, especially when plankton is abundant. Although it has hundreds of small teeth, it does not use them when feeding.

Behavior

The behavior of the basking shark is still unknown except for some information obtained from the observations. The motto of “basking” was got because it spends a long time feeding under the sun. One theory states that it prefers to feed in surface waters when there is abundant plankton in that part of the ocean, and at the same time it drops the spines of its gills. These are then renewed and so on, in a continuous seasonal process.

During the winter there are no sightings of basking sharks near the surface. Therefore scientists think that they migrate to deeper southern waters until the next summer. During this season many individuals are seen on the coasts of Iceland and northern Europe as they travel there to mate.

Its English name “basking shark,” means “taking the sun”.

The sturdy body and slow movements of the basking shark are not an impediment to jump out of the water trying to shed its parasites. It is also a relatively social animal because sometimes it forms small groups divided according to sex. Sometimes, they can form schools of up to 100 members.

Its English name “basking shark,” which means “taking the sun,” comes from its habit of swimming very close to the surface with the dorsal fin out of the water.

Reproductive Habits

The basking shark is ovoviviparous and reaches sexual maturity when it reaches a particular size; The male can reproduce if it already has a length of 1.5-1.8 meters and the female reaches sexual maturity when it has a length between 4 and 5 meters.

The type of reproduction, it is believed to be ovoviviparity. Fertilization is internal, and the embryos develop within the mother’s body in a yolk sac and without placental attachment. It is very likely that unborn babies practice oophagy.

Researchers are not yet sure of the length of the gestation period. The most accepted theory is that it lasts one year, but can be extended to 2 or 3 years. There is also no accurate knowledge about the number of offspring delivered, but once a pregnant female found had six developing pups inside, so perhaps the number is not very large. Once born, the little ones move away from the mother to start living on their own.

The basking shark gives birth only once every two to four years and its life expectancy is 50 years.

Threats and Conservation

The fishing of this shark has been very frequent for several centuries to obtain and to trade the meat, the oil, the liver, the cartilage and the fins. The oil, liver, and fins are still valued today, and this has caused serious problems for the survival of this shark that the IUCN Red List classifies it as a “Vulnerable” species.

For about 20 years, populations have drastically reduced and have not recovered yet. Fortunately, the situation put some countries on alert, and the species is now under protection in territorial waters of some countries like United States, United Kingdom, and New Zealand. Also, the commercial fishing of this species is banned in many regions.

Sources:

http://www.nefsc.noaa.gov/nefsc/Narragansett/sharks/basking.html

http://www.bbc.co.uk/education/guides/z94hvcw/revision

https://en.wikipedia.org/wiki/Basking_shark

http://www.iucnredlist.org/details/4292/0

http://www.arkive.org/basking-shark/cetorhinus-maximus/

https://www.flmnh.ufl.edu/fish/discover/species-profiles/cetorhinus-maximus

BioExpedition Publishing © 2017.

The “Prionace glauca” is a beautiful shark, with a blueish skin which gives it its common name. The term “glauca” comes from the Latin meaning “blue-gray” or “green.” It is the most distributed shark in the world.

It is a member of the order Carcharhiniformes, of the family Carcharhinidae and the Genus Prionace.

DESCRIPTION

The aerodynamic shape and lightness of the blue shark body allow it to move “elegantly” across the oceans. It exhibits countershading like many other sharks. The upper part is an indigo blue tone while the ventral and the sides are white.

It has a long caudal heterocercal fin. The second dorsal fin measures almost half the size of the first and its pectoral fins are unusually long compared to other sharks. Its eyes are large, its teeth are triangular, and it has a conical snout.

It reaches a length ranging from 3.8 to 4 meters and weighs about 240 kilograms. This species presents slight sexual dimorphism since the female tends to measure little more than 1 meter in comparison with the male.

It is the most distributed shark in the world.

DISTRIBUTION AND HABITAT

The blue shark inhabits in a great diversity of areas around the world. It dwells temperate, tropical and subtropical waters up to 350 meters deep. It lives near the coasts except those of Antarctica. It concentrates mainly in latitudes between 20 ° and 50 ° north and likes waters with temperatures of between 7 ° and 16 ° centigrade, although it can tolerate warmer temperatures slightly above 21 ° Celsius.

It fancies approaching the shores, where divers and boats see it often. It inhabits the epipelagic and mesopelagic zones near the coasts and the continental shelves, but if it dwells tropical waters, then it tends to go towards deeper waters.

FEEDING

It is a carnivorous predator that feeds on about 24 species of cephalopods and 16 species of fish. Its diet includes octopus, squid, mackerel, tunas, lobsters, crabs, small sharks and occasionally seabirds. They usually seek to catch small prey, but if they find large mammal carrion, it becomes part of their food.

The blue shark surrounds its prey before attacking it. When needed it joins with other sharks of the same species and cooperates to attack larger prey and facilitate their capture. Its swimming speed and its triangular teeth help this shark tearing the skin and flesh of the most complicated animals.

BEHAVIOR

It is a slow-swimming animal that increases its speed when feeling stimulated by external factors, such as the presence of animals from which it can feed on. If this happens, it then becomes one of the fastest fish.

The blue shark is nomadic and shows a clockwise migration pattern following the Gulf Stream to the Caribbean, passing along the coast of the United States, Eastern Europe, Southern Africa and back to the Caribbean.

REPRODUCTIVE HABITS

The Blue shark reaches sexual maturity at around 5 or 6 years old, after which can reproduce through viviparity. During the process of courtship, the male bites the female between the second and the first dorsal fin. Upon accepting, the male inserts its clasper into the female’s oviduct and transfers the sperm to fertilize the eggs. After mating both separate and do not join again, since this species is polygamous.

The frequency which females give birth or the time that the deposited sperm is stored after the intercourse is still uncertain, but the blue shark migrates northward to deliver their offspring. After a gestation period lasting between 9 and 12 months, the female gives birth to a large number of offspring. An unusual case was a mother that had 130 pups, but the average amount ranges between 25 and 50. Later, the newborns separate from their mother who does not provide any parental care.

The blue shark is not a regular victim of commercial fishing.

THREATS AND CONSERVATION

In contrast to other shark species, the blue shark is not a regular victim of commercial fishing although it is usually caught by fishing nets incidentally. Also, it is the target of sports activities in the United States, Australia and some parts of Europe.

As a consequence: the blue shark is “Near Threatened” according to the Red List of the International Union for the Conservation of Nature. Therefore, a group of organizations is committed to regulating fisheries and protecting the species, such as the International Plan of Action for the conservation and management of Sharks, the Sustainable Fisheries Act and the Code of Conduct for Responsible Fisheries from the Food and Agriculture Organization of the United Nations Fisheries and Aquaculture.

Some countries have banned shark finning, but still, there are not international treaties linking all aspects of blue shark protection.

Sources:

https://en.wikipedia.org/wiki/Blue_shark

http://www.iucnredlist.org/details/39381/0

http://www.arkive.org/blue-shark/prionace-glauca/

https://www.flmnh.ufl.edu/fish/discover/species-profiles/prionace-glauca

BioExpedition Publishing © 2017.

The bull shark is also known as the zambezi shark. It should not be confused with the sand tiger shark (Carcharhinus taurus), which is also called bull shark in other languages.

Many people consider the bull shark one of the most dangerous sharks in the world since this species has many attacks on humans registered, and according to the Internation Shark Attack File, it is the third species with most attacks on humans, only after the great white shark and the tiger shark. Besides, its aggressiveness and its ability to live in saltwater as well as freshwater, add further concern.

It is a member of the order Carcharhiniformes, Carcharhinidae, and Carcharhinus.

DESCRIPTION

The reason why it is called “bull shark” refers to the short, sturdy form of its body that resembles a bull, and perhaps it is also due to its hostile behavior. It has a blunt snout, rounded and wide but not very long. It has two dorsal fins with a triangular shape, of which the second is visibly smaller but the tips of both are dark in young specimens. They do not have an interdorsal ridge.

The reason why it is called “bull shark” refers to the short, sturdy form of its body.

Their eyes are quite small, which gives a clue about their limited visual sense and their preference for waters near the coasts where the prey are abundant. Instead, its movable jaws contain several triangular teeth that measure about 3 inches long.

The color of its skin is light gray, and its belly is white. There is sexual dimorphism: the female is larger than the male, as the male commonly has a length of 2.13 meters and weighs 90-95 kilograms, while the female reaches a length of 2.3-3.4 meters and weighs 129-230 kilograms.

DISTRIBUTION AND HABITAT

Bull shark distribution is along the coastal waters of tropical and subtropical seas around the world. In the Atlantic Ocean, it is located from the United States to Brazil and from Morocco to Angola. In the Indian Ocean, it is present in waters ranging from South Africa to Kenya and from India and Vietnam to Australia.

It is one of the few species of sharks prepared to inhabit saltwater and freshwater, in the latter for a long time. It dwells in waters ranging from 150 to 30 meters deep of oceans, seas, bays and harbors and even ventures into lakes and rivers.

Bull Shark – Carcharhinus leucas.

FEEDING

The bull shark is an opportunistic carnivorous predator but can eat almost anything it finds in its way including fish, rays, sea turtles, mollusks, echinoderms, young sharks (including the same species), mammals and seabirds. In the stomachs of some individuals have been found remains of hippos and humans but these are not a regular part of their diet. Their favorite fish are chelons, mullets, mackerels, and snappers. However, their food consumption adapts when they dwell in freshwater areas, and then feeds on turtles, shrimp and other species of that habitat.

It hunts only in murky waters and compensates its limited sense of sight with a keen sense of smell. If they find a suitable prey, they swim directly toward it reaching speeds of up to 19 kilometers per hour; it hits the victim, and then sink their sharp teeth into the flesh. The rest is already known.

REPRODUCTIVE HABITS

The bull shark is viviparous, and the age to reach sexual maturity depends on the geographic region in which it is located but usually the age is ten years old for males and 10.9 years old for females. Some individuals can mature when reaching eight years of age.

Mating occurs in late spring and the summer. The mating scars on the females’ body indicate that during the process, the male bites his mate.

The gestation period lasts 10 to 11 months. The female has between 1 and 13 offspring, often in brackish water or in freshwater lakes.

Probably their most notable behavior is that they can tolerate freshwater.

BEHAVIOR

The bull shark prefers loneliness than the company of other sharks of its species, so it hunts by itself. It is not migratory, but some individuals from South America travel thousands of kilometers to the Atlantic Ocean, and many often go to fresh and brackish waters to give birth.

Probably their most notable behavior is that they can tolerate freshwater. While their body adapts to this change (it reduces the amount of salt and urea to suit different salinities), it is surprising that they are not afraid of water systems that are less salty and more shallow than their natural habitat. They avoid regions with low temperatures.

It shows certain aggressiveness and tendency to live near populated areas, a fact that makes it an animal of care.

THREATS AND CONSERVATION

Commercial fishing usually does not try to catch bull sharks, but this species is classified as “Near Threatened” on the IUCN Red List without compelling reasons.

Over time it has been captured to obtain its meat, its skin and its oil for several purposes. Recreational or sports fishing is also responsible for the situation. In current times many aquariums demand the presence of the bull shark in their facilities since it is a species that adapts well to life in a closed environment and catches people’s attention. This practice still does not seriously harm shark populations but is a potential danger if demand increases.

On the other hand, roaming areas close to human populations makes it an animal more vulnerable to the effects of civilization, such as pollution and incidental fishing.

At the moment there are no specific programs, plans or actions for the conservation of the bull shark.

Sources:

http://www.iucnredlist.org/details/39372/0

https://en.wikipedia.org/wiki/Bull_shark

http://www.arkive.org/bull-shark/carcharhinus-leucas/

https://www.flmnh.ufl.edu/fish/discover/species-profiles/carcharhinus-leucas

http://animaldiversity.org/accounts/Carcharhinus_leucas/

BioExpedition Publishing © 2017.

Goblin Shark – Mitsukurina owstoni

Among all sharks, this species stands out for its unusual appearance characterized by a prominent snout. It is the only living member of the Mitsukurinidae family, and it is often called a “living fossil” since its ancestry goes back to the Cretaceous period and it keeps such primitive characteristics.

It was given a scientific name in honor of two people who collaborated in its discovery in the late nineteenth century: Kakichi Mitsukuri and Alan Owston. It belongs to the order Lamniformes and the genus Mitsukurina.

DESCRIPTION

The goblin shark differs from other shark species by having a flattened snout that protrudes from the top of its head, resembling the blade of a sword. Its jaws are protrusive, and the inside contains 35 to 53 rows of upper teeth and 31 to 62 rows of lower teeth. The length and width of its teeth are variable because those that are near the center of the jaws are longer than those on the back.

Has a flattened snout and its jaws are protrusive.

It has a thin body with a skin covered with dermal denticles. Its blood vessels are very close to the skin, which gives it a pink hue. It has five pairs of gill slits, two small rounded dorsal fins, short and wide pectoral fins, one anal fin smaller than the dorsal fin, and a caudal fin with a poorly developed lower lobe.

It is a medium-sized shark. The length of adults ranges between 3-4 meters, and the weight can reach 200-210 kilograms.

DISTRIBUTION AND HABITAT

Individuals of this species have been found in the Pacific Ocean, in the Indian Ocean, and in the Atlantic, so it is likely to have a global but non-uniform distribution. However, it mainly concentrates in waters of Japan, Australia, New Zealand, Guyana, Suriname, French Guiana, France, Madeira, Portugal, South Africa and the United States.

The sightings of goblin sharks are very rare and indicate that the species lives in waters on continental platforms and slopes, at depths of 1,300-1,370 meters.

FEEDING

The remains in the stomachs of several individuals captured reveal a carnivorous feeding based on teleost fishes, ostracods, squids, crabs, and cephalopods. Garbage and pelagic species have also been found in their bellies. Therefore this shark can swim in depths as well as on shallow waters to find food.

It detects prey by combining its senses of sight, smell, and electro-perception. If it is near the ocean floor and discovers a victim, it observes it from below without moving. It is not a skilled or fast swimmer, so it moves slowly towards its food to avoid being discovered.

The jaws of this shark have the ability to slide forward thanks to specialized joints that at the moment of biting are released from their tense condition and move abruptly and quickly to find the body of the prey.

BEHAVIOR

Although it is an efficient predator, it moves slowly, and that is why its hunting strategy is to wait until the prey is unaware. Their feeding based mainly on migratory fish suggests that many of the activities of this species occur during the nights or mornings.

Another method of finding food is moving the sand once it senses that something is beneath it. Probably the least used sense is the sight because it has tiny eyes.

It does not represent any danger to humans.

REPRODUCTIVE HABITS

There is a lack of information about the reproduction habits of the goblin shark since the sightings have been few and therefore, also the research. The few data available came from individuals caught accidentally and not from observations directly in their habitat.

Researchers believe it is ovoviviparous and migrates to mate or spawn as adult females gather in the east coast of Japan during the spring.

THREATS AND CONSERVATION

As it is rarely seen and captured, the goblin shark status in the Red List of the UICN is “Minor Concern.” Their few known threats are the accidental catch, mainly on the coasts of Japan. Besides, their strange jaws arouse curiosity to collectors who can pay from 1,500 to 4,000 dollars to get one.

Sources:

https://en.wikipedia.org/wiki/Goblin_shark

http://www.iucnredlist.org/details/44565/0

https://www.flmnh.ufl.edu/fish/discover/species-profiles/mitsukurina-owstoni/

http://australianmuseum.net.au/goblin-shark-mitsukurina-owstoni

http://animaldiversity.org/accounts/Mitsukurina_owstoni/

BioExpedition Publishing © 2017.

The shallow waters of the oceans disguise this shark characterized by the yellowish color of its back. It was first described in 1868 and was called Hypoprion brevirostris, but later Hypoprion was changed to Negaprion.

It is a member of the order Carcharhiniformes, of the Carcharhinidae family and the genus Negaprion.

DESCRIPTION

It is a big and robust shark with a nozzle shorter than the width of its mouth. It reaches a length of 2.4 to 3.6 meters and a weight of 90-183 kilograms being the female slightly bigger than the male.

It has a flat head, two large dorsal fins of similar size, one convex pectoral fin and one pelvic fin with concave back edges. The upper lobe of the caudal fin is larger than the lower. Its small eyes have a retina that has in the center a horizontal band useful to provide clear visibility under the water.

Its common name comes from the yellow or brown coloration of the back of its body. Thanks to this feature can camouflage perfectly with the bottom of the ocean in shallow waters because its color is similar to the sand of the sea floor.

The largest populations of this species inhabit regions of the Atlantic Ocean.

DISTRIBUTION AND HABITAT

The largest populations of this species inhabit regions of the Atlantic Ocean, but smaller concentrations also dwell in the Pacific Ocean. In the Nearctic realm of the Atlantic, they are distributed from the coast of New Jersey in the United States to the south of Brazil, passing through the Gulf of Mexico and the Caribbean Sea. To the east, they reside around the African coasts of Senegal and Ivory Coast. In the eastern Pacific, they are located from Baja California in Mexico to Ecuador.

This shark likes to inhabit coastal shallow waters. The usual depth in which they live is around 90 meters. They dwell areas with mangrove, coral reefs and can live in enclosed bays and even near the docks.

Although it is a saltwater species, it is possible that it wanders near the mouths of rivers. Its adaptability allows it to withstand deep water with little oxygen.

FEEDING

All sharks are thought to be opportunistic predators, but the lemon shark challenges this belief. This carnivore proves to have a preference for a particular prey and with a specific size, so its food is selective. In summary, it usually “chooses” animals not fast and medium-sized.

Their hunting technique consists in harassing the prey after detecting it. Quickly approaching it, and before making any physical contact, it stops abruptly. Then it hits the victim, holds it tightly around the head, and shakes it repeatedly until it can tear off pieces of flesh.

Their favorite preys are bony fish, mollusks, and crustaceans. Occasionally they catch seabirds and even other small sharks.

BEHAVIOR

The lemon shark can be solitary or show a social behavior by grouping with up to 20 members according to sex and size. Social interaction and group life seem to improve the processes of courtship, communication, predation and protection. Similarly, offspring have a higher chance of survival when living alongside other small sharks.

They exhibit a learning capacity from such interactions.

Research of the Negaprion brevirostris brain, show that the species has an apparent preference for social interaction, cooperation and the establishment of hierarchies of dominance and stable social relations. They also exhibit a learning capacity from such interactions.

It is an active animal during the day although it prefers to rest in silence in the bottom of the ocean. It sounds strange, but this activity requires more energy than swimming as it takes a lot of effort to pump water through the gills and avoid sinking. Their activity increases during the nights and mornings.

REPRODUCTIVE HABITS

This viviparous shark reaches sexual maturity at around 6.5 years old. The embryos develop inside the mother and feed on the nutrients from the yolk sac.

Before gestation, sharks mate during the spring and summer months. The fertilization is internal, and the wounds on the female’s pectoral fins indicate that the male bites her to hold it and insert its clasper. Apparently, the female stores the sperm of several males inside so there is sperm competition. That is why a single litter can have multiple paternity.

The gestation period lasts between 10 and 12 months. The female gives birth to 4-17 offspring and then waits one year to having offspring again. Meanwhile, those newborn stay in breeding areas until they reach a length of 90 centimeters.

THREATS AND CONSERVATION

It shares some threats with other shark species; its meat, liver, skin, and fins are highly valued in the gastronomic and medicinal fields. That is why there is an intense commercial and recreational fishing that negatively affects the survival of the species. Besides, it is in danger because its habitat of mangroves and shallow waters are devastated by human activities, mainly by constructions in the coasts.

Its conservation status is “Near Threatened” on the Red List of the International Union for the Conservation of Nature (IUCN). In this regard, there are no specific plans or programs for its conservation, but it has some protection from the United Nations International Plan of Action for the Conservation and Management of Sharks.

Sources:

https://www.flmnh.ufl.edu/fish/discover/species-profiles/negaprion-brevirostris

https://en.wikipedia.org/wiki/Lemon_shark

http://www.iucnredlist.org/details/39380/0

http://www.arkive.org/lemon-shark/negaprion-brevirostris/

BioExpedition Publishing © 2017.

The shortfin mako shark also is known as the blue pointer and bonito shark. It is a fast speed-swimming shark that has been called “the peregrine falcon of the sharks” in allusion to the fastest bird in the world. It is considered an animal dangerous to humans because of the speed which can attack and its ability to jump into the fishing boats.

It belongs to the order Lamniformes, the Lamnidae family, and the genus Isurus.

DESCRIPTION

The body of the mako shark is cylindrical, fusiform and hydrodynamic. There is sexual dimorphism since the female is visibly larger than the male. An adult can measure between 3.2 and 3.8 meters in length and weigh between 60 and 135 kilograms although females can reach 150 kilos.

The body of the mako shark is cylindrical, fusiform and hydrodynamic.

It has a powerful caudal fin semicircular with a highly developed lower lobe. It has two dorsal fins but the second one is much smaller than the first one, as well as two pectoral fins shorter than the length of the head. Its gill slits are long and have small black eyes; Young individuals have the tip of the snout black. Its teeth are large and very sharp, and they stand out when the shark closes the mouth.

Its body has a gray or metallic blue color on the dorsal area and a lighter color in the belly area.

DISTRIBUTION AND HABITAT

This shark inhabits all the temperate waters of the world, with larger concentrations in the Pacific, Atlantic and Indian oceans and in the Red Sea and the Mediterranean. In the Pacific, it is mainly located along the American coasts and from the Territory of Primorye in Russia to New Zealand and Australia. In the Indo-Pacific, it dwells from East Africa to Hawaii and in the Atlantic Ocean from the Gulf of Maine to Argentina and Brazil and from Norway to South Africa.

It is a pelagic species that occasionally approaches the coasts. Its natural habitat corresponds to tropical and temperate waters, epipelagic and coastal areas with depths up to 150 meters.

FEEDING

It is an efficient predator and therefore, a carnivorous animal that feeds on several species of fish, but certainly the favorite food of the populations who live in the Atlantic is the bluefish (Pomatomus saltatrix) that represents almost 92 percent of its total diet. Other common foods are cephalopods like octopus and squids, bony fish (mackerel, tuna, swordfish, etc.), dolphins, turtles, seabirds and small sharks. Every day, it consumes 3 percent of its weight and needs 1.5 to 2 days to digest its food.

When hunting, the mako shark stays under the prey after identifying it. Before the victim detects it observing its movements, the shark swims vertically toward the prey, immobilizes it by biting its caudal peduncle and begins tearing pieces of flesh.

BEHAVIOR

The mako is the fastest shark on Earth. It reaches up to 32 kilometers per hour with gusts of 72 km/h and is capable of traveling up to 55 kilometers in a single day. Therefore it shows signs of being a migratory species. This fish can also jump, as it has been seen doing it out of the water reaching up to 9 meters height.

Mako sharks are solitary individuals but may be grouped according to sex. It does not represent a grave danger to humans since it lives far from the coast.

Are solitary individuals but may be grouped according to sex.

REPRODUCTIVE HABITS

The female reaches sexual maturity when it equals a length of 3 meters, while the male can mate when it gets a length of 2 meters. It is a polygamous and polyandrous species that commonly form groups differentiated by sex, that is, males and females unusually get together if they do not have the objective to mate, which happens between late summer and early fall.

Many bodies of adult females exhibit scars on their bellies, flanks, and pectoral fins, indicating that perhaps the male is aggressive during mating. Either way, the male internally fertilizes the female, and the offspring develop inside the body of the mother (ovoviviparity). The gestation period lasts between 15 and 18 months, after which the female gives birth to a litter of 4 to 25 live offspring. The female waits about 18 months to get pregnant again, so it reproduces every 2 or 3 years.

THREATS AND CONSERVATION

The mako shark is an important species for commercial fishing. In addition to its flesh, fins, oil, liver, and cartilage, its jaws and teeth are decorative objects and even trophies. And like other species of sharks, it is a victim of bycatch.

The species is considered “Vulnerable” in the Red List of the International Union for the Conservation of Nature. As a consequence, some organizations have taken action on the matter in an attempt to protect and guarantee the survival of this shark species. For example, the United Nations Fish Stock Agreement (UNFSA), demands countries to create conservation strategies and follow the International Plan of Action for the Conservation and Protection of sharks, recommending a continuous assessment of the status of the shark populations, which also includes the mako shark.

Sources:

http://news.bbc.co.uk/2/hi/science/nature/3683885.stm

https://en.wikipedia.org/wiki/Shortfin_mako_shark

https://www.flmnh.ufl.edu/fish/discover/species-profiles/isurus-oxyrinchus

http://www.iucnredlist.org/details/39341/0

http://www.arkive.org/shortfin-mako/isurus-oxyrinchus/

http://animaldiversity.org/accounts/Isurus_oxyrinchus/

BioExpedition Publishing © 2017.