Stickleback is a name given to a family of small fishes of the Northern Hemisphere. They are called sticklebacks because some of their fins are made of strong, sharp, separated spines. Instead of having scales, the sides of the body may have a series of hard plates. There are both freshwater and ocean sticklebacks. The freshwater ones reach a length of 1 to 4 inches (2.5 to 10.2 centimeters). The ocean ones grow as much as 7 inches (18 centimeters) long. The brook stickleback is common in the interior parts of Canada and in the Great Lakes states. These fish, like other sticklebacks, build muff-shaped nests of sticks and roots for receiving the spawn (fish eggs). The male carefully guards the spawn. He also watches over the young for several days after the eggs hatch. Sticklebacks usually eat small invertebrates (animals without backbones), such as insect larvae and worms. They also feed on the eggs and young of other fish.
