Prior to the females arrival the males exert enormous energy building and protecting sites that will entice females. The better the spawning site the bigger the male protecting it. He must stay to occupy the area so he must find food there. When females arrive males will no longer feed. They court the females and exhibit what a fine nesting site they have.
Females look around and the same pecking order as the males occurs.
The better the site the bigger the females. The females lay their eggs and the male fertilizes them. Even if the female is 20 pounds heavier than the male she will be driven from the nest. Males threaten and beat the females away from the nest. Normally the bigger females are rammed till bruised to force them away.