Sicyopus discordipinnis
Sicydiine gobies, or “cling gobies,” are a subfamily (Sicydiinae) of around 80–90 species in eight genera, more than half described only in the last twenty years. Every species is amphidromous: adults live and spawn in fast, clear freshwater streams, but the tiny hatchlings are swept out to sea, where they spend a planktonic larval phase before returning to fresh water as post-larvae — often in a synchronised pulse the day after a full moon — and migrating back upstream, sometimes climbing waterfalls along the way using a sucking disc formed from fused pelvic fins. Most species graze algae and biofilm from rock surfaces using a distinctive fleshy sac of replacement teeth above the upper jaw, and males in breeding condition are typically brilliantly coloured, in sharp contrast to drabber females. All Australian cling gobies are protected species — look, but don’t touch.
Species Summary
A microcarnivore reaching about 65 mm total length, Sicyopus discordipinnis occurs in Australia, New Guinea, New Hanover and Bougainville, with Australian records confined to Noah Creek and Pauls Pocket Creek in the Daintree area of far north Queensland. Displaying males show grey stripes turning jet-black with orange-to-red colouration developing over the posterior body.
Compiled for Home of the Rainbowfish from ANGFA sources: A. R. Tappin, “Australian Sicydiine Gobies”, In-Stream 23, 2014, pp. 12–18; G. R. Allen, “Unexplored islands of Papua New Guinea”, Fishes of Sahul 17, 2003, pp. 926–948.