Sperm motility of sooty grunter, Hephaestus fuliginosus (Macleay), and jungle perch, Kuhlia rupestris (Lacépède), in different salinities

Abstract

The spawning habitat of jungle perch is unknown. It coexists in the short, fast-flowing freshwater streams of north-eastern Queensland with sooty grunter, a known freshwater spawner. The duration and intensity of sperm motility in various dilutions of sea-water were compared to indicate whether jungle perch spawn in fresh water or salt water. Sooty grunter sperm was most active in salinities of 0 g l^-1 and 5 g i^-1, and not motile in salinities above 15 g l^-1. Jungle perch sperm was not motile in fresh water, but most active in 25 g I^-1. These results, together with fish distribution studies in estuaries, indicated that jungle perch probably spawn in the sea in salinities above 25 g I^-1..