Female mate choice through spawning parade formed by male-male competition in filefish Rudarius ercodes

In the small filefish Rudarius ercodes inhabiting temperate seaweed beds, 2-10 males follow a gravid female, in a line until spawning early in the morning. Formation of the spawning parade and change of male order were investigated in a large aquarium. Males competed for the position nearest to the female during the parade, while the female controlled the parade by her swimming speed and course. During the parade, male members and their order changed frequently. The male order in the parade was related with the intensity of nuptial coloration, which changed according to the social rank. The female sometimes tried to take a spawning posture but rejected spawning when male positioning was not good for her, for example, far different from parading order. The female spawned with 2-5 males on each side. The nearest mating positions to the female were usually occupied by two males that had been staying at an anterior position in the parade for a long time. During the spawning parade over a long distance and time, females of R. ercodes can choose multiple suitable males in a variable environment like a temperate seaweed bed.