The rock goby, Gobius paganellus, is a small coastal fish of eastern Atlantic waters, from Scotland to Senegal. It is also reported from the Mediterranean and Black Seas, and is a Lessepsian migrant in the Gulf of Eilat and Red Sea. There are unconfirmed records from the area around Pointe Noire in the Congo Republic.
The rock goby is usually black with white blotches - although the male is much more black when guarding the eggs. There is a pale band on the top of first dorsal fin. The rock goby grows to 12 cm in length.==Habitat== The rock goby prefers rocky sea floors below the low tidemark, although it can be found in larger rock pools in Summer. It may also live in fresh or brackish water. Its usual depth range is from 3 to 15 metres.==Behaviour== The rock goby eats small crabs and amphipods, polychaetes, larvae and small fish. The juvenile diet includes Calanus, a copepod, and mites.==Reproduction== The rock goby reproduces in Spring. It nests in rocky areas near the kelp forest, Up to 7000 eggs are laid, in a single layer, under rocks and shells. The eggs (up to 7000) are laid in a single layer (2.5 mm in height) and guarded aggressively by the male. The eggs hatch in about 19 days.