Polygamy in the mottled sculpins (Cottus bairdi) of southwestern Montana (Pisces: Cottidae)

Abstract

Relationships among nest sites, guardian male size, and male courtship success (number of matings per male) were examined in 11 populations of mottled sculpins (Cottus bairdi) in the Madison River in southwestern Montana during the 1978 and 1979 breeding seasons. The number of matings per breeding male ranged from 1 to 12. Sites used as nests were not a random sample of available sites but were larger than average-sized rocks on the stream bed. Larger males had larger nest sites. Male courtship success was sometimes correlated with nest size. The best predictor of male mating success was male size. These observations are consistent with the hypothesis that polygamy in mottled sculpins has evolved through female choice, not through resource defense.