The Southern Cardinalfish,
Vincentia conspersa, is one of the 'usual suspects' lining up under South Australian jetties.
What is unusual about this fish and its close relatives is that the male is completely responsible for brooding the eggs until hatching.
During brooding the male will keep the clutch of eggs in it's mouth and not eat until they have hatched.
This guy under Pt Hughes jetty is clearly single and out for a good time.
Photo: Robert Rath, 'Day 729, The Cardinal' 1/100s f/18 ISO320 100mm