Bull Sharks

1. Bull Sharks Matthew Phung & Brittney Coffer

2. General Information • Names-Bull sharks, Carcharhinusleucas ,aka zambezi, ganges (often confused with the Ganges river shark, Glyphisgangeticus), ground sharks, river sharks, freshwater whalers, and estuary whalers • Size – The Bull Shark’s maximum length is 11.5 feet (350 cm). Birth length is 29 inches (75 cm). Females tend to grow larger than males averaging about 8 feet long. • Weight- The Bull Shark’s average weight is over 500 pounds (230 kg). • Description-They are gray on top and white below, and the fins have dark tips, particularly on young bull sharks. They haveshort, broad, blunt snouts, small eyes, and triangular saw-edged upper teeth. • Teeth-Bull shark teeth are triangular, serrated (saw-edged), and very sharp. The teeth are located in rows which rotate into use as needed. The first two rows are used in obtaining prey.As teeth are lost, broken, or worn down, they are replaced by new teeth come into place.

3. Habitat • 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. 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. • The bull shark is a widespread coastal and freshwater shark.They have a unique ability to penetrate far up rivers. They have often been found hundreds of km from the sea in the Amazon River and the Nicaraguan Lake. They range from the western Atlantic to the eastern Atlantic; The Indo-West Pacific to the eastern Pacific. Bull sharks are the most common of about 6 species of shark in their genusthat can travel between salt and fresh water or live in fresh water for prolonged periods.

4. Life History • Bull sharks are estimated to live to the age of 24. Adults apparently leave the lagoons after giving birth. Juveniles remain in lagoons and near shore coastal waters until reaching the age of maturity. The use of different habitats by adult and juvenile sharks is thought to be an adaptation that helps improve the survival of young sharks through a decreased risk of being preyed upon by the adults. • In the western north Atlantic off Florida and the Gulf of Mexico, and off South Africa, the young are born in late spring or early summer. Off Nicaragua, females may have young throughout the year, with a peak in spring and early summer.

5. Diet • Bony fishes and small sharks. • In the western Atlantic they commonly feed on mullet, tarpon, catfishes, menhaden, gar, snook, jacks, mackerel, snappers, and other schooling fish. • Other food items in bull sharks include sea turtles, dolphins, crabs, shrimp, sea birds, squid, and dogs. • Rays seem to be particularly important components of its diet as well. • Invertebrates including, crabs, shrimp, and sea urchins have been identified in stomach contents.

6. Behavior • Bull sharks are massive and fearsome sharks with a pugnacious attitude. • One of the top three to attack humans. • When they attack humans it’s usually inadvertent or out of curiosity rather than intended prey. • Bull Sharks tend to attack humans in estuaries and bays because the bull shark swims in shallow water, as do we. • WE invade their territory and they attack sometimes to defend what is theirs. • The bull shark, like the tiger shark, is known to be extremely opportunistic and versatile in its feeding habits.

7. Reproduction • Maturity- Age of maturation of Bull Sharks varies according to geographic location. Examples:Gulf of Mexico found that the age of maturity was 10 years for females and 9-10 years for males. They are able to reproduce between the ages of 6-15. • Mating- In the Gulf of Mexico mating occurs during summer months, and the pups are born the following April-June. Mating and birthing occurs year-round in the warmest parts of the bull shark's range. Females often bear mating scars on their dorsum. • Gestation- Bull sharks are viviparous with a yolk-sac placenta, and give birth to 1-13 young per litter. The pups are nourished internally by the mother for 10-11 months, and they then give birth to live, free-swimming young in nursery grounds near Estuaries and river mouths

8. Attacks • Along with the Great White and Tiger Shark, the Bull Shark is responsible for the most accidents involving people. • Most attacks aren’t fatal, but the loss of limbs and occasional death is due to the bacteria that grows in the teeth of these sharks. • More likely to be struck by lightning than attacked by a shark. To Avoid attacks • Avoid swimming near river mouths or other estuaries with turbid waters where bull sharks are known to occur • Do not swim near schools of fish in inshore areas. These schools are often pursued by large predators

9. INTERESTING FACTS • A Bull Shark can survive in freshwater as well as in salt water. In freshwater it creates 20 times more urine than a similar Bull Shark in salt water. • They are hunted all over the world commercially and are sold fresh, frozen, and finned for shark fin soup, hides for leather, liver for oil, and carcass as fish meal. • Got their name from their short, blunt snout as well as their tendency to head butt their prey. • The role they play in their habitats is the “top predator” and as the population decreases, their prey- cownose rays- increase and are wiping out scallops. (keystone species)

10. Bibliography • http://digitalcommons.unl.edu/ichthynicar/38 • www.flmnh.ufl.edu • www.marinebio.org • www.nmfs.noaa.gov