© Shutterstock-Aleron Val A small, scaleless fish species The stickleback is a small, scaleless fish found in the fresh, brackish, and marine waters of the Northern Hemisphere’s temperate regions. These tiny fish grow average 5-10 cm (2-4 inches) in length and include about eight fish species within the Gasterosteidae family. Cousins to the pipefish and seahorse, sticklebacks are identifiable by a row of 2 to 16 spines in front of their dorsal fin. The three-spined and nine-spined sticklebacks are more commonly seen species, occurring throughout the Northern Hemisphere in fresh and saltwater. The brook and four-spined sticklebacks thrive in the freshwater environments of North America, while the 15-spined stickleback is found off the coasts of the British Isles and northwestern Europe. Check out the map below to find out where sticklebacks are seen at dives sites near you.