Density Dependent and Density Independent Regulation of Reproduction in the Gila Topminnow, Poeciliopsis Occidentalis (Baird and Girard)

Studies of the Gila topminnow, Poeciliopsis occidentalis, indicate that onset of reproduction, proportion of reproducing ♀ ♀, and numbers of embryos carried by ♀ ♀ are influenced by H2) temperature, photoperiod, food, and predation. Water temperature and photoperiod act upon the fishes regardless of population density, whereas, nutrition influences and predation are proportionate to population density. Therefore, density dependent and density independent factors operate to regulate reproduction and neither is mutually exclusive.