|| 要旨トップ | 目次 |||日本生態学会第59回全国大会 (2012年3月，大津) 講演要旨
一般講演（ポスター発表） P2-328A (Poster presentation)
Introduced species increase their individual numbers partly because they are released from the predation pressure by their natural enemies. Contrarily, bluegill Lepomis macrochirus was often introduced to water bodies in Japan together with its predator, largemouth bass Micropterus salmoides. To understand how bluegill can become dominant under the pressure of largemouth bass whereas most of native fishes decreased, behavioral reactions by bluegill to the visual cues of largemouth bass were compared to thoes by two native cyprinids (Nigoro-buna Carassius buergeri grandoculis and Abura-boteTanakia limbata) in aquariums, where prey fish were separately kept in the transparent glass case. Although time periods spent for being inactive, hovering and swimming were all different among three prey fishes, the effect of presence of the predator was not clear. Bluegill showed so-called death mimicry, more frequently when they are alone than when in a group (even when the predator was absent). Once largemouth bass approached to prey fishes, only bluegill seldom changed its behavior, while two native fishes suddenly dashed to escape from or follow the predator. Probably as a result, only half of approached bluegill was attacked by the predator, whereas most of approached native fish were attacked. Remaining inactive may be important to avoid predation of largemouth bass.