Abstract
Males of the goby occupy the nests with a small entrance and brood periodically in semilunar cycles. We investigated the preference of males to the shape of nests using the brooding periodicity and experimental nests with various sizes of body and various sizes of entrance. Brooding in semi-lunar cycle and sharper hatching peaks indicate that the timing of releasing of larvae must be precise for their reproduction. Males appear to select the nests by means of not nest size, but entrance size, even though large nests have a larger capacity of eggs than small ones. The analyses using the selection order index, SOI, showed the same results. Our observations show that one of the reasons why they need the nest with small entrance should be intrusion of sneakers.
