The body shape in males and females is subtly different. The female is less compressed than the male, has a rounded form by comparison, and is a little deeper overall, often with a pronounced bulge of the chest. The male is slimmer, and far more compressed. The bulge in the chest is absent, and he may only be two thirds the width of a comparative female of the same length, and consequently weigh far less. The males head is quite pointed and the snout appears slightly upturned, whilst the females head is rounder and with a snub nose. In the breeding season males become covered in tubercules and often display a reddish flush on their bellies and intense vermilion pectoral and ventral fin colouration, whilst all other fins can become very dark and opaque. The females at the same time, can become very rotund and deep set.