Diets of scaup occupying baitfish and sportfish farms in eastern Arkansas

Abstract

Although not typically associated with eating fish, lesser scaup (Aythya affinis) and greater scaup (Aythya marila) have recently been reported consuming large quantities of bait- and sportfish produced on Arkansas commercial aquaculture facilities. During winters 2016–2017 and 2017–2018, we collected 529 lesser scaup and 19 greater scaup foraging on golden shiner (Notemigonus crysoleucas), fathead minnow (Pimephales promelas), goldfish (Carassius auratus), sunfish (Lepomis spp.), and other sportfish production ponds to investigate the diet composition of scaup. We compared lesser scaup diet between years, among temperature categories (Low, Medium, High), and among pond types using PERMANOVAs to investigate foraging dynamics. Lesser scaup diets differed between winters, and between Low and both Medium and High temperature categories. Only traces of fish were detected in scaup in winter 2016–2017, but fish comprised 18% of birds' overall diet in winter 2017–2018. Chironomidae was the most common prey item in lesser scaup during both winters, occurring in 86% and 68% of diets in winter 2016–2017 and 2017–2018, respectively. Chironomidae comprised 40% of lesser scaup diet by weight in winter 2017–2018, but 71% in winter 2016–2017. Similar to lesser scaup, Chironomidae was the most commonly occurring prey item in greater scaup, which occurred in 88% of the diets, or composed 74% of their overall diet. Fish comprised about 13% of the overall diet of greater scaup. We suspect that scaup increasingly exploited fish in colder winters, perhaps because of the birds' increased energy demands, prey availability, and ease of capture, or some combination of these.