10 20 40 60 cm
mittakaava < 10 cm
Wilhelm von Wright: Pohjolan kalat, Lauri Urho, Petri Savola (Uudenmaan ympäristökeskus). All rights reserved.
- Other names: Ninespine stickleback, Ten-spined stickleback
- Family: Sticklebacks and tubesnouts – Gasterosteidae
- Similar species: brook stickleback, three-spined stickleback
- Size: 3-5 cm.
- Appearance: As in other sticklebacks, the body of the nine-spined stickleback tapers to a very narrow caudal peduncle leading to a fan-shaped caudal fin. The nine-spined stickleback is the smallest of Finland’s sticklebacks. Resembles its three-spined cousin but body not as deep. The most reliable means of identification is, of course, the number of spines in front of the dorsal fin, which varies from 7-12, though there are usually nine. Small bony plates found only on narrow caudal peduncle at lateral line. No scales. Mouth pointed upwards.
- Colouring: Greyish or olive green, sides slightly silvery, translucent. Sides have irregular dark bars or blotches. At breeding time males become almost black, only the pale spiny pelvic fins showing up.
- Reproduction: Spawns in June-July along shallow, weedy shorelines. The male marks out a territory, which he defends aggressively. He builds a nest using pieces of plant material into which he entices females through an elaborate courtship procedure. After fertilising the eggs the male stands guard, occasionally fanning them with well-oxygenated water until they hatch after about a week. He remains to guard the young until they have used up the contents of their yolk sacs and move away to fend for themselves.
- Food: Plankton and small bottom invertebrates.
- Distribution and habitat: Common along all Finland’s coasts and inland waterways, including most lakes. Prefers nutrient-rich waters with plenty of shallow, weedy margins. Tolerates low oxygen levels fairly well. Outside the breeding season nine-spined sticklebacks move in small shoals along the shoreline and sometimes out in open water in search of plankton.
Despite being such a common fish, few people will have seen the nine-spined stickleback as it seldom turns up in the usual fish traps and nets.