I've never heard of Ring-necked Ducks feeding on 'minnows'. I rank this duck just below Canvasbacks and above Lesser Scaup and Redheads, as table fare. Indeed, Clarence Cottam shows their diet to be overwhelmingly plant material (82%), with another 10% insects. Mollusks make up most of the remainder and fish are not mentioned at all. Here in the fall they commonly feed on crustaceans (brine shrimp) in beds of sago pondweek along with the scaup in our formerly brackish or subsaline lakes that are now filled with freshwater fish. Canvasbacks and swans ate the sago tubers while scaup and ringnecks ate the shrimp.

https://naldc.nal.usda.gov/download/CAT86200638/PDF