We identified species and approximate size of prey items in 109 digital photographs of North American River Otters (Lontra canadensis) hunting in a 2-km stretch of South Fork Eel River, California, from January 2017 through December 2021. Over the 5-y study, 403 observations of River Otter social-group types and sizes were recorded, including singles, family groups with pups, and groups of up to 8 adults. An average of 3.0 River Otters per week (s_x = 0.2, range 1 to 13 individuals) were observed in the study area. Eleven species of prey were taken by River Otters, including primarily, Sacramento Pikeminnow (Ptychocheilus grandis; 54.1% of 109), followed by crayfish spp. (24.8%), Pacific Lamprey (Entosphenus tridentatus; 10.1%), herpetofauna (6.4%), and less-frequently taken fish species (4.6%). Contingency table frequencies indicated Sacramento Pikeminnow and crayfish were taken more in months of low water flows in the river. Herpetofauna prey included 1 American Bullfrog (Lithobates catesbeinus), 2 Foothill Yellow-legged Frogs (Rana boylii), 1 Northwestern Pond Turtle (Actinemys marmorata), and 3 Rough-skinned Newts (Taricha granulosa), apparently with no ill effects to the otters. Sacramento Pikeminnows were captured by social groups of 2 and 3 or more River Otters more often than expected, and by single otters and family groups less often than expected; whereas crayfish were captured by single otters and family groups more often than expected, and by social groups of 2 and 3 or more, less often than expected. Different River Otter social-group types and sizes captured smaller (<30 cm) and larger fish (≥30 cm) at similar frequencies.