Food Habits of Carp and White Suckers in the South Platte and St. Vrain Rivers and Goosequill Pond, Weld County, Colorado

Gut contents of carp (Cyprinus carpio Linnaeus) and white suckers (Catostomus commersoni [Lacépède]) collected by electrofishing from the South Platte and St. Vrain rivers, and Goosequill Pond near the Fort St. Vrain Nuclear Generating Station, Colorado, were analyzed by standard means to determine food habits. Chironomid larvae and pupae were the principle foods of both fish species in the streams. Carp and white suckers competed for this primary food source; both fish species fed primarily on chironomids and did not feed effectively on tubificid worms. White suckers supplemented their diets with species of Simulium, Hydropsyche, Hyalella and terrestrial invertebrates. Carp were more opportunistic and consumed more of the less-abundant food organisms than suckers did. Both streams supported limited numbers of benthic invertebrates. Consequently, large quantities of algae, sand, detritus, and terrestrial invertebrates were found in the gut contents of both fish species. Carp in Goosequill Pond fed primarily on chironomids but also consumed many entomostracans and crayfish.