In this study, we investigated mating system and mate choice of the triplefin blenny Enneapterygius etheostoma on a rocky reef at Banda, Tateyama Bay, Chiba, Japan, from 21 May to 19 July 2020. The larger males maintained a territory, while the smaller ones joined reproduction as a sneaker. The females visited the territorial males to spawn. The mating success of each territorial male was evaluated by the number of females the...