Bull Shark

The Bull shark (Carcharhinus leucas) is also called the Zambezi, Ganges (which is actually Glyphis gangeticus), Ground shark, River Shark, Freshwater Whaler, Estuary Whaler, Shovelnose, Slipway Grey and Swan River Whaler. Bull sharks are very robust-bodied and have a blunt, rounded snout. They lack an interdorsal ridge. The first dorsal fin is large and broadly triangular with a pointed apex. The second dorsal fin is significantly smaller. The pectoral fins are also large and angular. Bull sharks have relatively small eyes as compared to other carcharhinid sharks, which suggests that vision may not be as important a hunting tool for this species which often occurs in turbid waters.

It is reported that some shark attacks attributed to Great White's may actually be Bull shark attacks. They are considered to be the third most dangerous species to humans.

Bull sharks are pale to dark gray above, fading to white on their underside. In younger individuals the fins have black tips which fade to a dusky color as they grow.

The maximum reported length of the bull shark is 11.5 feet (350 cm), weighing over 500 pounds (230 kg). Size at birth is around 29 inches (75 cm). Females grow larger than males, averaging 7.8 feet (240 cm) as adults, weighing around 285 pounds (130 kg). This is the result of a longer lifespan of about 16 years, compared to 12 years for males. Males average 7.3 feet (225 cm) and weigh 209 pounds (95 kg). Growth rates calculated from captive bull sharks were estimated to be about 11 inches (28 cm) per year in the first years of life, slowing to half that rate after about 4 years of age.

Bull sharks occur in tropical to subtropical coastal waters worldwide as well as in numerous river systems and some freshwater lakes. They have been reported 3700 km (2220 mi) up the Amazon River in Peru, and over 3000 km (1800 mi) up the Mississippi River in Illinois. A population in Lake Nicaragua (Central America) was once thought to be landlocked, but they gain access to the ocean through rivers and estuaries. In the western Atlantic bull sharks migrate north along the coast of the U.S. during summer, swimming as far north as Massachusetts, and then return to tropical climates when the coastal waters cool.

The bull shark prefers to live in shallow coastal waters less than 100 feet deep (30 m), but ranges from 3-450 feet deep (1-150 m). It commonly enters estuaries, bays, harbors, lagoons, and river mouths. It is the only shark species that readily occurs in freshwater, and apparently can spend long periods of time in such environs. It is not likely that the bull shark's entire life cycle occurs within a freshwater system, however. There is evidence that they can breed in freshwater, but not as regularly as they do in estuarine and marine habitats. Juvenile bull sharks enter low salinity estuaries and lagoons as readily as adults do, and use these shallow areas as nursery grounds. They can also tolerate hypersaline water as high as 53 parts per thousand.