This body shape poses a minimum amount of resistance as water flows over it. You can tell a lot about a fish s habitat by the shape of its body. Tuna, which are extremely fast, are shaped like torpedoes. Fish that live in strong flowing streams, like trout and many species of minnows, also have torpedo-shaped bodies that allow them to navigate strong currents. The elongated bodies of eels and other snake-shaped fish are perfect for slithering through holes or among bottom vegetation, but are not good for fast swimming.
Some shapes have little to do with efficient movements.
A number of fishes have rigid, even hard bodies and are decidedly unstreamlined. We have chosen the bluegill, the rainbow trout, the bluefin tuna and some microscopic animals for the exhibits on movement. Lurking in weed beds and under ledges, these freshwater predators peer out and lunge for smaller fish or a fisherman s bait. Also lurking in the same places are largemouth bass. Like all sunfishes, the bluegill uses its tail like a fan to dig out a nest in the bottom of a stream or lake.