Some kinds of fish can change their gender from male to female. How does this ability aid the fish?

Since one male can mate with several females it helps the fish by having a higher percentage of females to continually produce young. The male can keep mating until he dies then one female comes out of production and becomes the next male.Some kinds of fish can change their gender from male to female. How does this ability aid the fish?
well to start,this was also MY d. science question...........and it said that its because of the reproduction and that certain fish change male to female but one type of specie cannot go back to its original gender............but yea. hope that helps....a lil'

bye. skatechic....

{who goes to the sk8 park like everyday}