The stickleback is a well-known fish, and is the archetypal 'tiddler', the first small fish caught by many school children (4). It is a small, beautifully streamlined, torpedo shaped fish, with a broad tail fin. Although most individuals tend to measure between 4 and 6 cm in length (2), some marine sticklebacks may grow to 10 cm (3). The common name derives from the most unique feature of these fish, the presence of two to four, but typically three, sharp spines on the back in front of the dorsal fin (3). The sides of this stickleback are usually covered with large bony plates; this armour is more developed on individuals living in the sea than freshwater sticklebacks (2). The back is dark grey, greyish or bluish-green, and the flanks are silvery (2). During the spawning season, males develop a metallic sheen and a prominent bright orange or red colouration on the front part of the underside (2).
- Length: 4-6 cm (2)