Simon actually did some serious thinking the other day after my blog on the rarity of sexually selected characters in marine systems. He came up with a couple more examples of sexual selection, one of which was the difference between the sexes in mandarin fish. Mandarin fish males are much larger than females and have very elongated fin rays. Males behave differently from females, arriving at the mating grounds well before females do, securing and defending small territories in the broken Acropora rubble mandarin fish mate above.
Males compete fiercely over the ownership to especially attractive sites. Conflicts are most often resolved by a side by side measuring of each others strengths, where obviously weaker fish fold before fighting, as fighting would not do them any good anyway. However, at times the male pair will be more or less evenly matched and a vicious fight can be initiated, where males push, flick and bite each other.