Ask Dr Dazza | Bull Sharks

Published 4:07pm 24 February 2021

Ask Dr Dazza | Bull Sharks
Words by Dr Dazza

BULL sharks have increasingly become a target for recreational fishers in Moreton Bay, and some anglers specialise in their capture during summer and early autumn.

They belong to the large group of sharks commonly called “whalers”.

Sharks are ancient animals; they were around before the dinosaurs and obviously outlived them. In fact, they have survived five mass extinction events.

Bull sharks, tiger sharks and white sharks are the three species most frequently responsible for serious bites on people and fatalities. Deaths from bull shark bites have occurred in Moreton Bay and the Brisbane River.

The average maximum size of a bull shark is 2.4 m and 130kg, with females reaching a slightly larger length and weight than males. Larger ones up to 4m have been recorded though. Weight for weight, bull sharks have the highest bite force compared to other shark species including white sharks.

The habitat of bull sharks is wide ranging from the open ocean to freshwater rivers. Large bull sharks can move over a large geographic area, but they may also spend extended periods of time at a single location and this is thought to be related to prey availability.

Pregnant female bull sharks move into estuaries and near coastal areas to breed during the warmer months. Bull sharks, like most sharks, give birth to live young. They are termed ovoviviparous – there is internal fertilisation, but the female shark does not directly nourish the developing offspring. This is different to most mammals including us. A bull shark pup can be 60-80cm at birth with litter size varying from five to 14. The length of pregnancy for a female bull shark is about 12 months.

Young bull sharks use rivers and estuaries as nursery areas. They can live in freshwater or brackish areas for long periods of time. This means they can grow in an environment, where the chances of becoming prey for larger sharks is reduced. It is only when they grow, that they develop the ability to use marine waters more effectively.

Bull sharks are opportunistic feeders and what they eat depends on their size and location. They are very effective at hunting in murky waters. They feed on a wide variety of fish and stingrays. They also scavenge and are known to feed on marine mammals, marine turtles and sea birds. They have been recorded as scavenging on terrestrial mammals such as cows and horses that have been washed into rivers during floods or other events.

If fishing for bull sharks, remember there is a maximum size of 150cm and a bag limit of one per person or two per boat with two or more people on board.


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