The absence of large blotches indicate the similar Rock Goby. These smudges are obscured in breeding coloration of both G.niger and G. paganellus and sometimes at other times. Rock Goby, Gobius paganellus . Colour scheme, size and habitats are the same as the Dragonet, Callionymus lyra . Spring around the British coasts.
Male fish turns a blacker tinge when guarding the nest.
The third spine of the first dorsal fin is longer than the others and this is never the case with the similar Rock Goby. 32-45 scales on the lateral line, less than the Rock Goby. In sandy areas, usually with rock as well, below low water mark and sometimes found intertidally in large pools. The adults are found at low water mark in late summer and autumn. Small crustaceans, worms, small fish.