Rock Goby
 

Common Name(s): Rock  Goby  Scientific Name: Gobius paganellus Family: Gobiidae  Usual Size:  12 cm    to 35 g  Photograph by  Andy Horton

Identification: 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 or transparent fringe to the first dorsal fin is distinctive.                                                Photograph by Darryl Mayer                                         Click on the image for more information   The black spots on the side of the body are always small and never big black smudges. The large blotches are characteristic of the Black Goby. The black dots are obscured in breeding coloration of both G.niger and G. paganellus and sometimes at other times.  50-58 scales on the lateral line, a greater number than in the similar species.  Similar Species: Black Goby, Gobius niger. The species has been confused in books, and probably in reports as well, with the rare (in British seas) and considerably larger Giant Goby, Gobius cobitis.         Black Goby Black Goby Rock Goby   Photographs by Richard Yorke Presence of black sensory papillae on the head of the Black Goby is an excellent ID character.  ID help by Lin Baldock Note the absence of black papillae on the Rock Goby. There appear to be black smudges.  Breeding:  Spring around the British coasts. The eggs are laid on the underside of rocks and shells. Male fish turns a pronounced black when guarding the eggs, as can be seen in the photograph by Andy Horton below. The pale band on the top of first dorsal fin sometimes has an orange tint.  On the Sussex coast the adults guarding the eggs can be found from the equinoctial low tide and below, in rocky areas adjacent to the kelp forest zone, during the spring, March (preparing to guard the eggs) and April especially. The eggs (up to 7000) are laid in a single layer (2.5 mm in height) and guarded ferociously by the male (it may kill rivals and even larger fish of different species in aquaria). The eggs will hatch in about 19 days (depending on temperature). (One record of a successful hatching known).  Food of the larval fish includes Calanus nauplii. (see Russell p. 264)  Habitat: In rocky areas below low water mark and commonly found intertidally, especially the juveniles. The adults are found at low water mark in spring and in large pools throughout the summer. First year fish can even be found under rocks on the shore in winter when all other fish are absent (Sussex).  Food: Small crustaceans, worms, larvae, small fish (including other species of gobies). Range: Off the coasts to the south and west of Britain only. English Channel but absent from the North Sea.  Additional Notes: Common.  Information wanted: Please send any records of this fish, with location, date, who discovered it, how it was identified, prevalence, common name and any other details to Shorewatch Project EMail  Glaucus@hotmail.com.  All messages will receive a reply.    Shorewatch Project Link:  Gobies1.htm Information supplied by Andy Horton (British Marine Life Study Society)  Differences between Blennies & Gobies Gobies are difficult to identify. Photographs in books cannot be relied upon because the identifications of British species are wrong over 50% of the time.