10 20 40 60 cm
mittakaava < 20 cm
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Wilhelm von Wright: Pohjolan kalat. All rights reserved.
- Other names: Butterfish
- Family: Gunnels – Pholidae
- Slightly similar species: four-bearded rockling, snake blenny, viviparous blenny
- Size: Usually 15–20 cm.
- Appearance: Body elongated, eel-like. Vent roughly half-way along body. Body rather flattened. Long dorsal fin extends from just behind head and has soft spiny rays. Anal fin reaches to mid-point of body. Caudal fin rounded, clearly distinguished from dorsal and anal fins. Pelvic fins very small. Head rather small with lower jaw protruding and mouth turned upwards. The small scales are difficult to see under the slimy skin covering.
- Colouring: Brown, often with yellowish markings forming a regular pattern. Dark vertical line below eye. The most characteristic feature of the rock gunnel is the row of 9-13 dark spots, each surrounded by a pale yellow ring, along the base of the dorsal fin. Spots absent from very small individuals.
- Reproduction: Little is known about how the rock gunnel reproduces in the Baltic Sea. Thought to spawn during winter, the eggs being laid on the underside of a shell or under a stone in a nest prepared by the male. The male remains to guard the eggs, fanning them with his tail.
- Food: Small benthic organisms and fish roe.
- Distribution and habitat: Found in coastal waters from Sipoo (east of Helsinki) to Kaskinen on the Gulf of Bothnia, and in the waters around the Åland islands. The rock gunnel is a bottom-dweller, inhabiting water less than 10 m deep. Hides under stones or weed during the day, emerging at night to seek its prey.