Food and Feeding Behavior of the Shovelnose Sturgeon, Scaphirhynchus platorynchus, in the Unchannelized Missouri River, South Dakota

The feeding habits of the shovelnose sturgeon (Scaphirhynchus platorynchus) were investigated in the unchannelized Missouri River, South Dakota, between October 1971 and September 1972. The annual diet was dominated by aquatic arthropods, particularly larvae of the insect orders Trichoptera, Diptera, and Ephemeroptera. The annum feeding behavior was separated into three intervals: (1) the fall months, during which the fish extensively utilized the major components of the drift; (2) the winter period, characterized by exploitation of a greater diversity of aquatic and terrestrial invertebrates; and (3) the late spring and summer interval, in which feeding was restricted to benthic foraging. Electivity values indicated opportunistic feeding activity. Shifts of feeding activity were influenced by timing and rates of discharge from the Lewis and Clark Reservoir located upriver. Changes in the elevation and velocity of the water mass appeared to affect the vulnerability of prey organisms.