| Affiliation: | (1) National Research Institute of Fisheries Science, 1088 Komaki, Ueda, Nagano 386-0031, Japan;(2) Japan Society for the Promotion of Science Domestic Research Fellow, 1088 Komaki, Ueda, Nagano 386-0031, Japan;(3) Field Science Center for North Biosphere, Hokkaido University, N9 W9, Sapporo 060-0809, Japan |
| Abstract: | Food niche variation within a population of white-spotted charr, Salvelinus leucomaenis, was investigated by means of mark and recapture to examine the simplification that conspecific individuals are ecologically equivalent. Food diversity measured on the basis of living form of dietary organisms demonstrated variability in food niche in incidence, degree, and stability. As inferred from body size distribution and fish movement, niche variation was inexplicable by social rank hierarchy or foraging habitat rotation, and occasional niches were deemed to be realized individually. Higher annual growth rate shown by those with a larger niche width indicated the adaptive significance in niche variation. Assuming trade-off between feeding efficiency and predation risk, phenotypic plasticity was suggested to determine the food niche specialization of individuals to maximize lifetime fitness. |
