Bull Shark, Carcharhinus leucas Valenciennes, 1839

Introduction

The Bull Shark is one of the few sharks that are potentially dangerous to people and is probably responsible for most of the shark attacks in and around Sydney Harbour.

The species is also the only widely distributed shark that stays in fresh water for long periods of time to feed and breed. Females sometimes give birth in river mouths where the young will live for up to 5 years.

3D interactive model of Bull Shark

_{3D model made by cdmstudio.com.au}

Identification

The Bull Shark can be recognised by a combination of characters including a stout body, short blunt snout, triangular serrated teeth in the upper jaw and no fin markings as an adult. The species has a second dorsal fin about one third the height of the first, a small eye, and no skin ridge between the two dorsal fins. It is grey above and pale below, sometimes with a pale stripe on the flank.

Habitat

The Bull Shark can live in a wide range of habitats from coastal marine and estuarine, to freshwater. It has been recorded from the surf zone down to a depth of at least 150 m. It is the only species of shark that is known to stay for extended periods in freshwater. It has been reported nearly 4000 km from the sea in the Amazon River system, and is known to breed in Lake Nicaragua, Central America.

Distribution

This species has a widespread distribution in tropical and warm temperate waters worldwide. In Australia the Bull Shark occurs from south-western, Western Australia, around the northern coastline and down the east coast to the central coast of New South Wales.

The map below shows the Australian distribution of the species based on public sightings and specimens in Australian Museums.

Feeding and diet

Bull Sharks have an omnivorous diet which includes fishes (including other sharks), dolphins, turtles, birds, molluscs, echinoderms and even terrestrial mammals including 'antelope, cattle, people, tree sloths, dogs and rats’ (Compagno, 1984; 480).

Life History

Bull sharks are born at between 55-80 cm and grow to ~340 cm TL. Female and males mature at about 220-230 cm TL at around 20 years of age, living for approximately 50 years.

Females generally give birth to litters of between 1-13 pups in estuaries and river mouths where the young stay for about 5 years before spending time in their preferred environment of close inshore lagoons, bays, coastal channels and river mouths.

Danger to humans

The Bull Shark is an aggressive species that is considered dangerous to humans. Some authors consider that the Bull Shark may be more dangerous than the White Shark and the Tiger Shark. This is because of the Bull Shark's omnivorous diet and habitat preferences. The species may be found in murky water, where the splashing of a swimmer could be mistaken for a struggling fish.

The 2.8 m long fish in the images was caught on 18 February 1999, in a commercial fishing net near Grotto Point, Middle Harbour (Sydney Harbour) by T. and V. Depasquale and S. Virtu. This catch was a most unusual occurrence which attracted significant media interest. The specimen was on display at the Sydney Fish Markets for a week (where the images were taken) before it was donated to the Australian Museum by G. Costi (De Costi Seafoods). The specimen is now registered in the Australian Museum Fish Collection (AMS I.39432-001).