The Rock Goby (Gobius paganellus) can grow to 12cm.
Medium-sized goby (a family of small fishes with a notorious reputation of being difficult to differentiate, characterised by a pair of dorsal fins, and a pelvic fin fused into a weak suction cup). The first dorsal fins are never elongate in this species (see Gobius niger). Black with white blotches which makes it appear grey. In breeding coloration the white and orange fringe to the first dorsal fin is distinctive.(see picture)
Black Goby, Gobius niger'.
Spring around the British coasts.
In rocky areas below low water mark and commonly found intertidally, especially the juveniles. The adults are found at low water mark in spring abd in large pools throughout the summer.
Small crustaceans like caprellids, worms.
Off the coasts to the south and west of Britain only. English Channel but absent from the North Sea.
The Aquarium Project