Adults inhabit the sea for an undetermined period and are parasitic on fishes; enter freshwater to breed. Majority of adulthood is spent in estuaries or at sea. Upstream spawning migrants occur in fast-flowing sections of rivers with a mud, sand or silt substrate, sometimes seen congregated below barriers to upstream movement such as weirs. Ammocoetes live in slow-flowing streams, burrowed in mud or silt. Common length is 35-40 cm (Ref. 44894).