Trophic polymorphism in bluegill sunfish (Lepomis macrochirus) introduced into Lake Biwa: evidence from stable isotope analysis |
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Authors: | Kimiko Uchii Noboru Okuda Ryuji Yonekura Zin’ichi Karube Kazuaki Matsui Zen’ichiro Kawabata |
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Affiliation: | (1) Center for Ecological Research, 2-509-3, Hirano, Otsu, Shiga 520-2113, Japan;(2) Gifu Prefectural Research Institute for Freshwater Fish and Aquatic Environments, Gifu, Japan;(3) Research Institute for Humanity and Nature, Kyoto, Japan |
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Abstract: | Trophic polymorphism was recently reported in introduced bluegill (Lepomis macrochirus) in Lake Biwa, Japan, where three morphs are specialized in benthic invertebrates (benthivorous type), submerged aquatic plants (herbivorous type), and zooplankton (planktivorous type). We evaluated the long-term effects of food resource utilization by these trophic morphs using stable isotope ratios, δ15N and δ13C. A significant difference in δ15N was found between the benthivorous and planktivorous types. The planktivorous type had the higher δ15N value, which corresponded with the value expected from its prey, zooplankton. The lower δ15N value of the benthivorous type would be derived from the lower δ15N values of benthic prey organisms compared to zooplankton. These results support previous findings that the benthivorous and planktivorous types have different food resource utilization. In contrast, the δ15N and δ13C values of the herbivorous type were distinctly different from the expected values, indicating that this type was unlikely to utilize aquatic plants substantially, contradicting the results of the dietary analysis. |
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Keywords: | Trophic polymorphism Introduced bluegill Food resource utilization Stable isotope |
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