Foraging ecology of Bowfin (Amia calva), in the Lake Huron–Erie Corridor of the Laurentian Great Lakes: Individual specialists in generalist populations

Abstract

Abstract The foraging ecology of bowfin (Amia calva) is relatively unknown in the Laurentian Great Lakes despite comparable abundances to other piscivorous predators. We investigated bowfin foraging ecology by determining trophic position, isotopic niche size, dietary proportions, and the degree of individual specialization at two locations in the Lake Huron–Erie Corridor using carbon (δ13C) and nitrogen (δ15N) stable isotopes and stomach content analysis. Trophic position did not differ between Mitchell's Bay (4.2) and Peche Island (4.3) using δ15N, but both sites had large ranges in individual estimates (range = 2.8). Bowfin isotopic niche size was large across site, season, and tissue, suggesting a generalist feeding strategy at the population level. However, bowfin had greater between-individual than within-individual variation accounting for 72% and 88% of total niche size at Mitchell's Bay and Peche Island, respectively, suggesting specialist feeding strategies at the individual level. Stable isotope mixing models for Peche Island showed high proportions of crayfish (54%) and small fish (Cyprinidae spp., Lepomis spp.; 38%) in their diet, consistent with high stomach content prevalence for crayfish (spring = 75%, fall = 10%) and small fishes (spring = 19%, fall = 33%) at Peche Island. Overall, our analysis of bowfin suggests a complex foraging ecology with bowfin acting as generalist predators at the species level but exhibiting a high degree of individual specialization, warranting further study to assess their trophic role in this diverse ecosystem of conservation concern.