Trophic polymorphism in introduced bluegill in Japan

Authors

  • Ryuji Yonekura,

    1. 1Center for Ecological Research, Kyoto University, Kamitanakami, Otsu, Shiga 520-2113, Japan and 2Lake Biwa Museum, Oroshimo-cho 1091, Kusatsu 525-0001, Japan
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  • 1 * Katsuki Nakai,

    1. 1Center for Ecological Research, Kyoto University, Kamitanakami, Otsu, Shiga 520-2113, Japan and 2Lake Biwa Museum, Oroshimo-cho 1091, Kusatsu 525-0001, Japan
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  • and 2 Masahide Yuma 1

    1. 1Center for Ecological Research, Kyoto University, Kamitanakami, Otsu, Shiga 520-2113, Japan and 2Lake Biwa Museum, Oroshimo-cho 1091, Kusatsu 525-0001, Japan
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*Author to whom correspondence should be addressed. Email: yone@ecology.kyoto-u.ac.jp

Abstract

We demonstrate that bluegill (Lepomis macrochirus) introduced from their native North American source to Lake Biwa in Japan showed considerable trophic and morphological variations (morphs). Three morphs were found for larger bluegills, specialized in three distinct resources (i.e. plankton, benthic invertebrates and aquatic plant), and two morphs were found for smaller bluegills, specialized in two slightly different prey taxa (i.e. calanoid and cyclopoid plankton). These morphs, especially for the large size class, can be distinguished primarily by differences in midbody length and depth. The dietary specialization and morphological differentiation among individuals were considered to be a result of different requirements for efficient resource utilization, which is a unique example of trophic polymorphism occurring in an introduced fish species in a species-rich fish community.

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