Type locality, Hong Kong, ZMM P3123 (holotype Triaenophorus trigonocephalus) (Ref. 075154). Reported from Sharp Island (Ref. 94637); Tung Ping Chau (Ref. 119714); Starfish Bay, Kei Ling Ha Lo Wai, Nam Wai (Ref. 125515); and Cape D'Aguilar (Ref. 129329). A single individual was also reported from Sham Chung. May be more common in estuaries and shallow coastal waters (Ref. 128523). Juveniles were recorded from Ma Shi Chau and Lai Chi Chong (Ref. 125536). Also enter freshwater: reported from streams at Tung Chung, Tai Ho, and Sup Long in Lantau Island (Ref. 129476).