北海道朱鞠内湖水系におけるイトウの生活史に沿った食性と生態的地位の変遷

抄録

Changes in dietary habits and ecological niche of the Sakhalin taimen Parahucho perryi were estimated from the analyses of carbon and nitrogen stable isotope ratios in the Shumarinai Lake system, Hokkaido, Japan. Stable isotope ratios of both elements in 0+ fry in a feeder stream were within the range of stable isotope ratios in other fish species collected from the same stream, although nitrogen stable isotope ratios in co-existing 1+ juveniles were 0.84‰ to 2.10‰ higher than in the latter. Nitrogen stable isotope ratios in large individuals (54.5–69.5 cm fork length) in the lake were 1.40‰ to 4.28‰ higher than in other fishes. These results suggest that Sakhalin taimen begin predating other fishes at the 1+ juvenile stage, with larger individuals becoming a top predator in the Shumarinai Lake system.