This superb shark is one of the largest species. Easily recognizable, its silhouette is massive and very streamlined. It has a fine, pointed and heterocercal caudal fin, that is to say asymmetrical with a larger upper lobe, and strongly dimensioned pectoral fins of triangular shape. Its brown / gray body with metallic reflections is streaked with dark vertical stripes degrading towards the abdomen like the tiger, hence its name. The stripes are more visible, darker and more marked in juveniles than in adults. Its muzzle is short and rounded, underlined by long nasolabial furrows. The growth of the tiger shark is variable, like all sharks, depending on its environment. Indeed, if the latter evolves at shallow depths in areas protected from predators where food is scarce, such as lagoons and sandy bottoms, it will have a slow growth and rapid weight gain thanks to the economy of its energy. On the other hand, we will find the opposite phenomenon in those who grow up on the high seas. A rapid growth with a slow weight gain due to a daily expenditure of energy. By default, tiger sharks in the open sea, in South Africa for example, are longer and smaller than coastal tiger sharks, in the Bahamas for example. It is the only one, among carcharinidae, to be ovoviviparous. Of the "genre" Galeocerdo, this automatically classifies it in another genre.
Habitat
The tiger shark lives in all temperate and tropical seas. It is found from surface to about 350 meters deep, near shorelines and continental shelves. However, it seems to prefer murky waters near ports, estuaries and sewage exits. However, it is also observed in quiet lagoons and at the edge of the reefs.
Life mode
Tiger sharks are rather docile in nature and are very powerful swimmers. They live regularly on a very large area of evolution, their territory, deeper and less active during the day than at night. Most often, they move in deep water on the reefs during the day and close to estuaries in troubled waters at night. However, they are regularly observable at shallow depths during the day when they stay in areas suitable for breeding or parturition.
Food
The tiger shark has the characteristic of feeding on just about anything that comes within its reach. Omnivorous, it is also nicknamed the “trash” shark. It consumes turtles, dugongs, dolphins and other sharks, including its own species, as well as corpses and waste. It also swallows wood, plastic, tires and metal objects. The first observations of their long migration were made when an adult tiger shark was caught off Hawaii. His stomach contained California license plates! Bahamian tiger sharks do not migrate extremely far as they have an organized migration pattern around feeding points. The tiger shark is considered a "super-predator".
Dating with the man
Its nutritional and morphological characteristics, its size, make it one of the most potentially dangerous sharks for humans. The tiger shark is a tethered shark, hard to pin down! No creature in the underwater animal kingdom faces it. He does not fear anyone and is too often in the habit of touching and tasting, to see what happens next. He has no preliminary phase of approach and can change his attitude at any time! Extremely aggressive towards underwater hunters when baited, he prowls around his prey with increasingly tight circles. The tiger shark is part of the top trio with the Great White Shark (Carcharodon carcharias) and the Bulldog shark (Carcharhinus leucas). It is the shark responsible, along with the bulldog shark, for the greatest number of attacks on humans throughout the tropical zone.
However, the tiger shark scuba diving which is marketed and carried out in a good number of places is carried out in 99% of cases by the practice of "feeding" and "baiting". These techniques which aim to attract the shark in the area where the diver immerses only reveal a small number of accidents, less than ten / year, despite the reputation of our terror of the seas! However, it is recommended, when diving, to display the greatest caution and the greatest respect for safety instructions. Because indeed, this shark is no less unpredictable! In certain circumstances, if you find yourself underwater with several specimens, even if the broom of their approaches remains almost constantly the same, they will not hesitate, if they feel it, to take the upper hand in order to to drive you out of the area, especially if territorial behavior takes hold between them.
Observation N ° 1
The tiger shark does not react in the same way according to the regions, the age and the number of individuals. Indeed, his behavior will be different if the shark is alone or in number, if he is accustomed to divers or not, and if he evolves with humans on the surface, scuba diving, close to the surface or more important depths. As described above, the attitude of the shark will not be evaluated in the same way if it is nurtured (encounter provoked), or during an unprovoked encounter. The tiger shark could be described as "primitive" in terms of its approaches because, as the only representative of the Galeocerdo genus, its instincts have not changed much since the Jurassic period. He will remain receptive to changing situations, but will remain nonchalant. For example, if the shark does not evaluate an approach that is not very fearful, it will always continue in a slow or active way.
Observation N ° 2
Meetings with the "tiger" are multifactorial and take into account several important criteria depending on the situation.
- The diver's behavior (diver's position, calm, neutral, excited or panicked attitude)
- The spatial situation of the diver (in the blue, on the reef, under the boat or in the open sea)
- The depth of the diver (at the same level as the shark or above it or on the surface)
- The distance between the man and the animal.
During a feeding or baiting
Spatial situation and distance between diver and bait box:
-Never be between the shark and the box
-Never be behind the box in the direction of the current!
… You might be mistaken for a rival, because of the smell!
During an unprovoked meeting
Reasons for shark approaching the diver's area:
territoriality, curiosity, area of gathering, mating, resting or farrowing ...
The study of tiger shark approaches being long and complex, we will propose in the next Mag an article specifically dedicated to this subject.
Observation N ° 3: meeting places
Under food stimulation
- Bahamas / Gran Bahama / Tiger Beach (all year)
- South Africa / Umkomaas / Aliwal Shoals (January to June)
- Tahiti / the white valley (all year round)
Not provoked encounter
- Red Sea / Sudan
- Galapagos
- Caribbean
- Philippines / Tubbahata Archipelago
- Hawaii
- Polynesia
- New Caledonia
Threat to the species
Like all great sharks, the tiger shark is threatened by fishing. Every day, more than a hundred tiger sharks are killed and the species is now seriously threatened, even if its registration is unfortunately still not effective.
Photo: Simone Caprodossi
Steven Surina
Steven Surina is a diving instructor in the Red Sea. In this capacity, for a decade, he has accompanied cruises along the Egyptian, Sudanese and Eritrean coasts. He worked in partnership with the Italian publishing house “Magenes Editoriale” on the project of a collection of dive sites all over the Egyptian Red Sea as an author and illustrator. He wrote a dissertation on the behavior of oceanic sharks in 2008 and had interactive booklets on the protection and preservation of sharks distributed to Egyptian schools.
This is how he created, in 2010, Shark Education which offers shark diving trips whose objective is to help them get to know and understand them better.
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