Fourspine Stickleback, Apeltes quadracus
The fourspine stickleback has a slightly laterally compressed body, which does not have scales or bony plates. Its colour is an olive-green to brown, with darker patches on the sides. The head is pointed with a terminal mouth. There are four dorsal spines (sometimes 5), of varying heights and angled alternately left and right. The dorsal spines have a sail-like membrane and are angled to alternating sides. There are also spines present on the pelvic and anal fins. The caudal peduncle is narrow and long leading to a rounded caudal fin. The average size of the fourspine stickleback is about two inches.
The fourspine stickleback lives in fresh, brackish, and salt waters, where they feed mainly on plankton. Spawning occurs May through July, at which time spawning males pelvic spines take on a red colour. Like other members of this family, the male builds a nest from vegetation, courts females, and provides parental care for the eggs and young. The overall nest can consist of several nest stacked, and contain eggs from several females. The fourspine stickleback is likely to be preyed upon by larger fish and birds. It is also sometimes used as bait by anglers.