木津川下流域におけるコクチバス当歳魚の食性

抄録

Food habits of young-of-the-year (YOY) smallmouth bass (Micropterus dolomieu) were surveyed from late June to early August, 2019 in the lower Kizu River, Kyoto Prefecture, Japan, prey importance being evaluated using the Index of Relative Importance (IRI). Stomach content analyses of 83 individuals revealed that unidentified fishes (%IRI: 36.6 %) and mayflies (Baetis spp.) (%IRI: 34.6 %) were important prey items, with YOY smallmouth bass as small as 10–20 mm in standard length preying on fishes. The onset of piscivory at an early life stage, likely resulting in higher predator growth rates and lower winter mortality, may have aided the establishment of M. dolomieu in the Kizu River.