Sicyopterus is a genus of amphidromous gobies found in fast-flowing streams on tropical islands and coastlines across the Indo-Pacific. The atlas covers 5 species ranging from roughly 2–3 in, with records from Indonesia, the Philippines, India, Malaysia, Papua New Guinea, Sri Lanka, Australia, and Fiji. Like other sicydiine gobies, Sicyopterus species have pelvic fins fused into a sucker-like disc that lets adults cling to and climb wet rock faces, including waterfalls, as they move upstream from the sea, and a highly modified, sediment-scraping jaw lets them graze algae and biofilm from stone surfaces in strong current.
The genus has a distinctive amphidromous life cycle: eggs are laid in freshwater, but the larvae are swept downstream to the sea, where they develop before returning as tiny postlarvae to climb back upstream, sometimes scaling substantial waterfalls with the sucker disc. On several Indian Ocean islands, most notably Réunion and Mauritius, the upstream migration of Sicyopterus lagocephalus postlarvae, known locally as bichique, supports a long-standing traditional and commercial fishery, making the species better known as food than as an aquarium fish. Sicyopterus is rarely kept in the hobby outside specialist biotope and goby circles, given its need for strong current and a marine larval stage that is essentially impossible to replicate in captivity.
With two of the five atlas species rated Least Concern and three not yet evaluated, no acute conservation concern is flagged for the genus as a whole, though amphidromous island gobies are inherently vulnerable to dams, weirs, and other stream barriers that can block the migration their life cycle depends on.