Emerald Bowfin Amia Ocellicauda Ecology In Three Minnesota Lakes: Abundance, Age Analysis, Diet Composition, And Stable Isotope Food Web

Author

• Griffin Blegen

Date of Award

4-2026

Document Type

Thesis

Department

Biology

First Advisor

Andrew Hafs

Second Advisor

Shannon Fisher

Third Advisor

Alec Lackmann

Abstract

The Emerald Bowfin Amia ocellicauda is a predatory fish species native to Minnesota that has often been discriminated against. This research expands ecological knowledge of Bowfin in Minnesota and provides population data to guide future management. Bowfin were sampled in the spring of 2024 and 2025 and a multi-census mark–recapture model was used to estimate abundance in three lakes. Estimated populations were 196 individuals in Little Toad Lake (95% CI: 116, 242) or 4.4 fish/littoral ha (95% CI: 2.7,5.7), 657 in Lake Sarah (95% CI: 436, 1014) or 4.2 fish/littoral ha (95% CI: 3.0, 6.7), and 612 in Gun Lake (95% CI: 368, 861) or 5.2 fish/littoral ha (95% CI: 3.2, 7.2). A subsample of 146 Bowfin was collected for age, growth, diet, and stable isotope analysis. Lapillus otoliths indicated ages ranging from 2 to 33 years. All von Bertalanffy growth parameters differed by sex, with asymptotic lengths of 702 mm for females and 561 mm for males, and growth coefficients of 0.218 and 0.633. Annual mortality (2.5-6.5%) and recruitment (RCD = 0.02 – 0.30) were low across systems. Diet analysis showed Bluegill Lepomis macrochirus as the dominant prey item (%IRI = 34.7-78.2%). Bowfin (TPscaled = 5.5-5.9) and Northern Pike Esox lucius (TPscaled = 5.4-5.7) occupied lower trophic positions than Walleye Sander vitreus and Largemouth Bass Micropterus nigricans (both TPscaled = 6.2-6.6). Bowfin displayed the broadest isotopic niche (SEAc = 1.3-3.3), and niche overlap was greatest between Bowfin and Northern Pike (58.2-100%). Together, these patterns suggest Bowfin are a broad-impact predator that regulates forage communities and contribute to ecosystem balance.

Recommended Citation

Blegen, Griffin, "Emerald Bowfin Amia Ocellicauda Ecology In Three Minnesota Lakes: Abundance, Age Analysis, Diet Composition, And Stable Isotope Food Web" (2026). Biology Graduate Theses. 19.
https://pines.bemidjistate.edu/thesis-biol/19