Grey Reef Shark Swimming In Shallow Water

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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.

White Tip Reef Shark In Coral Reefs

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Whitetip Reef Shark Close-Up

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Blue sharks eat almost everything. However, they prefer some types of fishes and squids.

Among the regular fishes they eat are herring, silver hake, white hake, red hake, cod, haddock, mackerel, butterfish, sea raven, tuna, and swordfish.

Other occasional meals of the blue shark are seabirds, garbage, and carrion and they even eat small sharks sometimes.

Like other big sharks, the blue shark includes seals into its diet.

Links to other pages in this site

How Many Teeth Does A Great White Shark Have?
How Many Shark Attacks There Are In The World?
How Does Global Warming Affect Sharks?
Why Are People Afraid Of Sharks?
What Do Sharks Have Instead Of Bones?

Blacktip Shark – Carcharhinus limbatus

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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.

Blue Shark Diving

Blue Shark Adventure

Grey Reef Shark – Carcharhinus amblyrhynchos

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