The eel is a long, slimy fish that resembles a snake. There are about 600 types of eels in the world, and most live in the ocean. These salt water eels include morays, congers, and snipe eels. However, scientists know little about these eels. The most studied eels belong to a group often referred to as the "common eels." These eels can survive in both salt  and fresh water.

    Common eels include the American eel and the European eel. American eels live along the Atlantic coast of North America. European eels live along the Atlantic coast of Europe and also in the Mediterranean Sea.

    Both American and European eels begin their lives in the Sargasso Sea, an area of the Atlantic Ocean northeast of the West Indies. The female eel lays eggs in the Sargasso Sea in the spring. Each egg will hatch into a tiny, narrow larva, the next stage in an eel's development. The larva, called a leptocephalus, is very similar to a transparent willow leaf. As the ocean's currents carry it northward, it undergoes a metamorphosis (change in body form) and develops into a transparent, tiny, miniature eel, or known as the glass eel.

    By this time, the eel is now reaching North America or Europe, and it has developed some coloration, and is now known as an elver. Scientists believe that the male elvers stay in the salt water along the coast, while most of the females swim into rivers, and other bodies of water. Elvers are strong swimmers, which comes in handy, and the females may climb over waterfalls and dams to reach inland waters. The elver gradually begins to increase in its size and turns a dull, yellowish-green. It is now called a yellow eel. During this stage, which will usually last 7 to 10 years, the eel will finally reach its full size. Most females will grow 3 to 4 feet long, and most males only grow 1 and a half feet long. Eventually, the eel will go through another metamorphosis, and become an adult. The skin color on their sides turn silver, their eyes become larger, and they become sexually mature and able to breed. In this stage, it is called a silver eel. Each fall, numbers of silver eels group together and migrate to the Sargasso Sea to breed. During this migration, they may need to cross land that is blocking their path. Scientists do not know how they find their way to the Sargasso Sea, but some think it's because of their sense of smell. Others believe that they rely on ocean currents. Studies show that eels can detect weak electric currents that are generated by the movements of water. These currents may serve as navigational guideposts for the eels.

Common eels are considered delicacies in Europe and Asia. European and Asian fishing crews will harvest great numbers of eel each year. The eels are caught in very large nets or in some specially built cages. In the United States, eel fishing is only a minor industry.