Other small residents of streams that are usually present are frogs, salamanders, and crayfish. Their young, which have gills, live in the river until they emerge, gill-less, for their adult lives. Crayfish are small crustaceans that look much like lobsters. Most Americans think of crayfish as living only in the Mississippi River, in Louisiana, but a wealth of species of crayfish exist all over the world. The Chinese, the world's oldest and most talented aquaculturists, are raising crayfish for food.
Many worms are present, including flatworms, annelids, and nematodes.
Many organisms spend their lives attached to or inside the bodies other animals, and so will only be seen if you collect the animals or dissect them. The bald eagle, the osprey, the kingfisher, and the heron fish for their meals, and the American dipper is a short, fat bird that walks underwater, amid rushing torrents, to find its food. The spotted sandpiper of the Eastern U.S. is able to do this, too. Bears and wolves fish rivers for salmon, and other mammals that hunt for food in the river include the playful river otter, raccoon, and mink. You are most likely to detect the presence of all of these creatures by the impressions their paws leave in the mud beside the stream.