Eventually all the water from Maine's rivers, streams, and aquifers empties into the Gulf of Maine. The landward edge of the Gulf of Maine runs from Nova Scotia, Canada, to Cape Cod, Massachusetts. If we could drain off several fathoms of ocean water, we would see two shallow underwater banks. These form the outer edge of the Gulf of Maine. In the spring, rivers carry melting snow to the Gulf of Maine. This makes it colder, less salty, and more fertile than the deeper Atlantic Ocean. The rivers carry food - minerals and decaying plants - to the many microscopic plants and animals of the Gulf, plankton. A circular current called a "gyre" moves this rich "plankton soup" around the Gulf, like a giant spoon stirring a pot of stew. Huge tides, in places 40 feet high, also help to mix the waters of the Gulf. Food, plankton, fishes, and even pollution are spread throughout the Gulf of Maine. <br> Some of the animal plankton are actually baby crabs, starfish, lobsters, and just-hatched fishes. If they survive their floating stage they may grow up feed on other bottom-dwelling animals, such as mussels, ocean quahogs, sea urchins, and scallops. Fish that live at or near the bottom, such as, cod, haddock, pollock and flounder, are known as "groundfish". Groundfish and herring (young ones are called sardines) usually swim in large schools. Schooling helps to protect fishes from their ocean predators, but it's precisely what makes them appealing to fishermen! Fishermen have been harvesting the Gulf of Maine since before the Pilgrims landed at Plymouth Rock. <br> Undoubtably the most popular Maine seafood is the American lobster. Lobsters are not popular with each other. In fact, they attack and eat each other whenever they get the chance. <br> Marine mammals, unlike lobsters, are very sociable animals. Many different kinds visit the Gulf of Maine in the summer. Like other tourists, they enjoy the cool waters and the abundant food. For example, one can often see seals while visiting the northeast coastline. There are five species of seals that visit the Gulf of Maine: hooded seals, harp seals, grey seals, ringed seals and harbor seals. Harbor seals, found in Maine year-round, often migrate south for the winter. They return in the spring and the mothers give birth.