Dive with
Tiger Sharks

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Diving with Tiger Sharks

Tiger Sharks in South Africa are most often found on and just south of a section of Aliwal Shoal called Eelskin, as well as at Protea Banks. We regularly encounter Tiger Sharks of up to 5 meters in length while diving these areas during the summer months. One can also attract the Tiger Sharks at Aliwal Shoal by chumming the water with sardines.

To do this we launch early in the morning and spend half the day at sea and have a 90% success rate. Once the Tiger Sharks (and often other shark species as well) arrive, we cut the chumdrum free and drift dive with the Tiger Sharks at a depth of about 8 meters. This type of diving is not for the faint of heart - the sharks come in very close and you must be prepared to push them away from time to time.

Taxonomy
First described by Peron and Lessueur in 1822, the tiger shark was given the name Squalus cuvier. Later, Muller and Henle designated Squalus arcticus as the type species and suggested the name Galeocerdo tigrinus. Various synonyms have been used since including: Galeus cepedianus, Galeus maculatus, Carcharias fasciatus, Galeocerdo rayneri, Galeocerdo obtusus, and Carcharias hemprichii. The genus name Galeocerdo is derived from the Greek, galeos = "shark" and the Latin, "cerdus" = the hard hairs of pigs. The Tiger Shark is also known as leopard shark, maneater shark, spotted shark, alecrin (Spanish), amarillo (Spanish), amzani (Swahili), bhoavar (Gujarati), cabron (Spanish), cação cabeça-chata (Portuguese), carcharias (Greek), cucut macan (Malay), itachizame (Japanese), jaguara (Portuguese), jarjur (Arabic), jarjur knaza (Arabic), kethulam (Telugu), ma`o patapata (Rapa), mangeur d'hommes (French), mano pa'ele (Hawaiian), ma'o tore tore (Tahitian), marracho tigre (Portuguese), naiufi (Samoan), ngutukao (Maori), pating (Tagalog), pilithatte (Kannada), pulli sravu (Malayalam), qio saga (Fijian), requin demoiselle (French), requin tigre (Creole), requin tigre commun (French), requin-demoiselle (French), requin-tigre (French), squalo tigre (Italian), te babatababa (Kiribati), tiburón tigre (Spanish), tierhaai (Afrikaans), tigerhai (German), tigre (Portuguese), tígrisháfur (Icelandic), tiikerihai (Finnish), tijgerhaai (Dutch), tintorera (Spanish), tintureira (Portuguese), wulluven sorrah (Tamil), and zarlacz tygrysi (Polish).

Description
Probably the most easy to recognize of the requiem sharks, the tiger gets its name from dark black spots and vertical bars which run the length of the body. Pups have spotted markings that grow together to form stripes that fade with maturity - adults are gray-brown on top, with an off-white belly. Tiger sharks has a large, thick-body with a blunt snout and the mouth is large with long labial furrows. The first dorsal fin is much longer than the second and the caudal fin is long and pointed. There is a dermal ridge along the back between the 2 dorsal fins.They have large eyes and good eyesight, aided by a special gill slit (a spiracle) right behind the eye, which provides oxygen flow directly to the eyes and brain. It has electroreceptors sensitive to electric currents in the water, and a very good sense of smell. One of the largest sharks, the tiger shark commonly reaches a length of 325-425 cm (10-14 ft) and weighs over 385-635 kg (850-1400 lbs). Length at birth varies from 51-76 cm (1-1.5 ft). Males reach sexual maturity at 226-290 cm (7-9 ft), while females become mature at 250-325 cm (8-10 ft).

The largest specimens are believed to attain a length of over 5.5 m (17 ft) and weigh over 900 kg (2000 lbs). Tiger sharks have an average speed of 2.4mph. they can swim in fast bursts, but the speed can only be maintained for a few seconds.

Teeth
The tiger shark has very distinct dentition - extremely sharp, serrated, curved, triangular shaped teeth located in several rows inside the sharks jaw. The teeth are the same size and shape in the upper and lower jaws. The first two rows of teeth are used in obtaining prey, while the other rows are kept in reserve. As teeth are lost, broken, or worn down, they are replaced by new teeth that rotate into place.

Distribution & habitat
With the exception of the Mediterranean Sea, Tiger sharks are found in tropical and temperate waters worldwide. Reports of individuals from as far north as Iceland and the United Kingdom have been confirmed but are probably a result of roaming sharks following the warmer Gulf Stream north across the Atlantic. Tiger sharks undergo seasonal migrations. It is well known that they move into temperate waters from the tropics for the warmer months and return during the winter. These sharks also make long oceanic migrations between islands and are capable of travelling long distances in a short amount of time.

The Tiger shark has a tolerance for many different kinds of marine habitat but generally prefers murky waters in coastal areas. They are commonly found in river estuaries, harbours, and other inlets where runoff from the land may attract a high number of prey items. Shallow areas around large island chains and oceanic islands including lagoons, are also part of the tiger shark's natural environment. They can be found from the surface down to about 350 m (1100ft).

Tiger sharks are solitary hunters that feed primarily at night as the shark moves further inshore and closer to the surface. Tiger sharks are sometimes seen in groups of several but this is probably a result of congregations of food items in the vicinity.

Diet
Powerful and extremely fast when attacking it's prey, it will eat almost anything and is considered to be the most scavingous of all the sharks. Preferred prey varies depending upon geographical region but commonly includes moray eels and sharks smaller in size such as Grey Reef sharks, Hammerhead and even other Tiger sharks, dolphins, fish, turtles, crabs, clams, mammals, sea birds, reptiles and just about anything else that they can catch alive. It is not uncommon to find objects of human origin in this animal's stomach. One large female caught off the north end of the Gulf of Aqaba in the Red Sea contained two empty cans, a plastic bottle, two burlap sacks, a squid, and a 20 cm (8 in) fish. Garbage and refuse is often recovered from the stomachs of sharks caught in harbours and river inlets where it is commonly dumped into the water.

Reproduction
In the Northern Hemisphere, mating takes place between March and May and the young are born between April and June of the following year. In the Southern Hemisphere, it is believed that pupping occurs in November to January. Tiger sharks are solitary except during mating.

Tiger Sharks reproduce viviparously, which means that like mammals, the give birth to live young that have been nourished by a placenta. Litters are anywhere fro 10 to 82 pups and the completely independent pups are about 750cm or 2.5 feet at birth.

Some scientists believe that because of the large size of the young at birth, uterine nutrition is supplemented by 'uterine milk' secreted by the lining of the uterus. Tiger sharks may live to the age of 50 years.

Importance to Humans
The tiger shark is harvested for its fins and flesh. It's liver, which tends to have a very high vitamin A content, is used to produce vitamin oil while its thick, tough skin makes for quality leather. Beside its significance to the commercial fishery, the tiger shark is a highly sought after big game fish.

Danger to Humans
The tiger shark is second only to the white shark in number of reported attacks on humans. Although they occasionally attack people and is greatly feared, people are not sought out by sharks. Tiger sharks can be curious and aggressive towards humans in the water and must be considered with a great deal of respect.

Conservation
Both commercial and recreational fishing catch rates for this species in the mid-Atlantic region have declined since the mid- 1980's, indicating that fishing pressure has adversely affected the size of the population. In contrast, relative abundance and catch rates for this species noted by commercial fisheries observers, especially for juveniles, are much higher than in previous fishery-independent and fishery-dependent surveys.

The World Conservation Union (IUCN) presently lists the tiger shark as "Near Threatened" throughout its range. The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species.

Sources
www.fishbase.org
www.scholar.google.com
www.sharks.com
www.enchantedlearning.com
www.austmus.gov.au
www.flmnh.ufl.edu
www.boattalk.com
www.conservationinstitute.org