We catch four-spine and, more rarely, three-spine sticklebacks in both fresh and salt water. The four-spine stickleback has four dorsal spines – three separate and one at the front of the dorsal fin – and a rounded tail. Males have red pelvic fins. The three-spine stickleback usually have three spines – two separate and one at the front of the dorsal fin – and its tail is more squared off. Both fish are brown or olive green in color with variable markings on their sides. Neither gets much longer than two inches.
Male sticklebacks build nests with aquatic weeds and grasses, go through elaborate courtship displays to entice females to lay eggs in the nests, and then guard the eggs and newly hatched young from predators.