Bull Sharks

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Bull Shark: Osmoregulator Predator
Scott Marshall
English Composition: EN-101-15
Professor Craig Cushing
April 19, 2010

Outline
Thesis Sentence: Carcharhinus leucas also known as Bull Shark are unlike other sharks as they can tolerate fresh water and can travel far upstream in rivers. I. Introduction
A. Definition of Carcharhinus leucas, its class, subclass and physiology
B. Eytmology.
II. Common Names
III. Habitat
IV. Eating habits
V. Adaptability; osmoregulation
VI. Shark Attacks-Some attacks of bull sharks are blamed on the great white A. Some statistical information
B. The 1916 New Jersey shark attacks
VII. Conclusion
A. Staying safe in the waters
B. Further reading

Bull Shark: Osmoregulator Predator
The bull shark is one of the sharks that captures my interest because it can live and hunt in both oceans and rivers. The species is formally known as Carcharhinus leucas. It belongs to a class known as chondrichthyes /kan-drik-the-ez/. This class is comprised of cartilaginous fishes with well developed jaws which include sharks, skates, rays and chimeras. (Merriam-Webster's Medical Dictionary, Merriam-Webster, Inc.) Cartilaginous fish means their skeleton is made of cartilage rather than bone. (Kennedy, What is an Elasmobranch?)

They also belong to a subclass called elasmobranch /i-laz-me-brangk’/. (Merriam-Webster's Medical Dictionary, Merriam-Webster, Inc.) This sub class is defined as having five to seven gills, openings on each side of the fish, rigid dorsal fins, spiracles to help with their breathing, and scales. Their upper jaws are not fused to their skulls and they possess many rows of sharp teeth that can be replaced continuously. (Kennedy, About.com Guide)

The bull shark is known by many names worldwide. It has the name bull shark from its appearance of a short stub nose and aggressive reputation. (Curtis) It has also been called a variety of other names ranging from Zambezi shark, Van Rooyen’s shark, Ganges shark, Nicaragua shark, fresh water whaler and estuary shark to river shark, ground shark, cub shark and shovelnose shark just to name a few. (Curtis) It gets all these names from primarily two reasons. One reason is its looks. The bull shark has a very robust body and a blunt rounded nose. They have no interdorsal ridge. They also have relatively small eyes compared to other sharks. The first dorsal fin is large, pointed and triangular, while the second is very small. (Curtis)

The second reason, which is more interesting to me, is the environments they have been found in. While it is not a true river shark because it cannot live permanently in the fresh water environment (K.J. O'Driscoll), the bull shark can bread, hunt and dominate in fresh water surroundings all over the world.

Bull sharks live in both fresh water and salt water. They can live in rivers, estuaries and some lakes in Central America. In fact, some have been found up the Amazon River in Peru and in water over three thousand kilometers up the Mississippi River into Illinois. Once thought to be landlocked, a whole population of bull sharks in Lake Nicaragua accessed the ocean waters through rivers. In the western Atlantic waters along the US coast, bull sharks migrate north in the summer months as far up as Massachusetts. They return to the tropical areas when the waters cool down again. (Curtis) Off the Pacific coast, bull sharks are found from southern California to the Gulf of California. (Bull Shark)

Bull shark stay close to the coastlines in waters less than one hundred feet deep. They also can go as far deep as four hundred fifty feet. They often go into estuaries, bays, harbors, lagoons, and river mouths. It is the only shark species often is found in freshwater locations and can spend long periods of time in these areas. (Curtis)

The feeding habits of the bull shark vary depending on opportunity, size and location. Stomach contents...
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