PREDATION BY LESSER SCAUP, Aythya affinis, ON COMMERCIAL SPORTFISH FARMS IN ARKANSAS

Arkansas commercial sportfish farms are located in the heart of the Mississippi Flyway bottleneck, and are visited by large flocks of lesser scaup (Aythya affinis) each winter. These diving ducks have been observed in even greater numbers on Arkansas fish farms in recent years, and have been frequently seen feeding on sportfish. Additionally, hunters have observed many small fish in the digestive tract of lesser scaup following harvest. Fish losses by migratory birds represent significant annual losses in production and income for Arkansas sportfish producers. Freshwater aquaculture acreage is down 32% in the United States since 2005. More intense farming practices and reduced water acreage in production have likely facilitated the congregation of more lesser scaup on remaining available ponds. With nearly 90% of all freshwater aquaculture acreage located within the Mississippi Flyway in the US, it is likely more scaup are congregating at higher densities. A previous winter study focused on lesser scaup and their predation on Arkansas baitfish farms during the winter of 2014. A follow-up study was conducted on Arkansas sportfish farms. Lesser scaup were collected (100 total) with shotguns in February and March of 2015 at sportfish farms in Lonoke and Monroe counties. Prior to collection, ducks were allowed to forage 10-15 minutes. Upon collection, a syringe without a needle was used to inject 50 mL of 91% isopropyl alcohol down the esophagus of the duck to preserve any fish in the digestive tract. Ducks were then transported on ice to the UAPB Lonoke Fish Disease Diagnostic Laboratory and frozen until processing. The esophagus, crop, and gizzard of each duck were examined for the presence of whole fish or partially digested fish parts (Figure 1). Fish retrieved from ducks were identified, enumerated, and weighed. Whole or partially digested fish were observed in 62% of the ducks examined. The contents of the gizzards are being examined for fish bones, scales, and otoliths. Results of these analyses are still forthcoming and will be discussed in context of the relevance to the commercial sportfish industry.