Polygyny in the River Sculpin, Cottus hangiongensis (Pisces: Cottidae), with Special Reference to Male Mating Success

The river sculpin, Cottus hangiongensis, which is a rock-nest spawner and spawns during the period from late April to early June, was polygynous in the three rivers where it was studied. In a river population, no significant correlation was recognized between the size of nest rocks and the male's mating success (number of females which mated with a male). On the other hand, a significant correlation was found between male size and male mating success. Under experimental conditions with tiles of the same size, larger males mated with a larger number of females. These observations suggest that male size is the most important determinant of female nest-choice and of male mating success. Females appear to minimize the risk of egg-predation by mating with those males which have a large body size and may thus have a greater advantage in driving away predators. The evolution of polygyny in this species may be explained by a model invoking female choice of male.