Two alternative female tactics in the polygynous mating system of the threadsail filefish,Stephanolepis cirrhifer (Monacanthidae)

Reproductive behavior of the threadsail filefishStephanolepis cirrhifer was studied at Kashiwajima, southern Shikoku, Japan. This species spawned in pairs on the sandy bottom, the eggs being scattered over an area of about 15 cm in diameter and attached to sand particles. After spawning, males departed immediately, while the females remained at the site to guard the eggs for a few minutes. Thereafter the eggs were left unguarded for three days until hatching. Females spawned only once daily, whereas males mated with multiple females in succession. The reproductive males established territories, in which 1–4 resident females defended smaller territories from each other. The harem size changed according to some ecological conditions, such as population density. Moreover, the males also mated with visiting non-resident females. Thus, the two alternative tactics of females resulted in two mating patterns, haremic polygyny and female visiting of male territories, in a single population ofS. cirrhifer.