American White Pelican Consumption of Spawning Walleye

We quantified the consumption of fishes, with emphasis on walleye Sander vitreus, by American white pelicans Pelecanus erythrorhynchos (AWPE) in the Tamarac River, MN during spawning migrations. AWPE abundance was estimated via aerial surveys (n=7), which peaked at 1,198 birds (95% CI, 1,176-1,219). Foraging bird days occurring on the river was estimated at 15,618. Camera trap data revealed that nearly all foraging occurred between 2028 (95% CI, 2022-2035) and 0621 hours (95% CI, 0608-0635). Walleye comprised 99.4% of voluntary regurgitated fishes (n=166), and 100% of fish retrieved from APWE via stomach pump (n=23). Evidence that the mean length of consumed walleye (µ=464 mm, n=176) was higher than the mean length of walleye in the river, captured via fyke nets (µ=423 mm, n=961), is provided by a Wilcox rank-sum test (p < 2.2e-16). A higher proportion of females in consumed walleye (40%) than walleye present in the river (13%) provides evidence to suggest a selection for female walleye by AWPE may exist (X-squared = 21.4329, df = 2, p-value = 2.2e-05). Walleye consumption was estimated at 20,802 kg, using an AWPE daily fish consumption estimate from the literature, which represented 0.24% of Red Lakes’ 2014’s walleye natural mortality.