Stiphodon rutilaureus
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
An algal grazer to about 42 mm total length, Stiphodon rutilaureus was first recorded in Australia at Pauls Pocket Creek in 2007, and also occurs in Papua New Guinea, the Solomon Islands, Vanuatu, the Bismarck Archipelago and New Caledonia. Females show a distinctive “cherub-blotch” pattern; displaying males develop a black-bordered second dorsal fin with an extended filament, and show off a bright orange, light-blue-cheeked display.
The species’ discovery in Australian waters is documented through a genuinely collaborative email-thread reconstruction, with Paul Thuesen, Peter Unmack, Helen Larson, Christophe Mailliet and Glenn Briggs cross-checking field photographs from Fig Tree Creek and a creek north of the Daintree to confirm the identification. Helen Larson’s advice on collecting the genus has become something of a standing joke among those who have tried: “very, very, very fast, so you need small dipnets… or zap them with an electrofisher.”
Compiled for Home of the Rainbowfish from ANGFA sources: B. Hansen, “Stiphodons in Australia”, In-Stream 13, 2004, pp. 6–10; 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.