Increases in prey population size can affect the physiology and ecology of upper-trophic level organisms. This phenomenon is known as a bottom-up effect. For example, the increased abundance of prey resources can trigger physiological (internal) changes in predators, such as improvements in nutritional status. However, these physiological aspects of bottom-up effects have not been considered. In this study, we tested the hypothesis that white-spotted charr Salvelinus leucomaenis, a salmonid fish, increases body stores of omega-3 fatty acids, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), by preying upon stocked hatchery-reared masu salmon Oncorhynchus masou fry in streams. The dynamics of fatty acid contents in charr inhabiting salmon-stocked and unstocked streams clearly support this hypothesis: fatty acid contents (DHA, EPA, and total fatty acid) increased after stocking in stocked streams, but not in unstocked streams. In addition, DHA increased with increasing body size of white-spotted charr and vice versa for EPA. The impacts of human activities, such as fish stocking, on freshwater ecosystems are a matter of serious concern for conservation. Future attempts to gain a comprehensive understanding of the impacts of fish stocking should consider not only community ecology but also physiology.

猎物种群规模的增加会影响上层营养级生物的生理和生态。这种现象被称为自下而上效应。例如，猎物资源的增加可以引发捕食者的生理（内部）变化，例如营养状况的改善。然而，自下而上效应的这些生理方面尚未被考虑。在这项研究中，我们测试了这样的假设：白斑红点鲑（一种鲑鱼）通过捕食孵化场饲养的放养鱼，增加体内 omega-3 脂肪酸的储存，尤其是二十二碳六烯酸 (DHA) 和二十碳五烯酸 (EPA)。马苏鲑鱼Oncorhynchus masou在溪流中鱼苗。栖息在放养和未放养鲑鱼的溪流中的红点鲑中脂肪酸含量的动态清楚地支持了这一假设：在放养鲑鱼的溪流中放养后，脂肪酸含量（DHA、EPA 和总脂肪酸）增加，但在未放养的溪流中则没有增加。此外，DHA随着白点红点鲑体型的增大而增加，EPA则反之。人类活动（例如鱼类放养）对淡水生态系统的影响是保护领域严重关注的问题。未来全面了解鱼类放养影响的尝试不仅应考虑群落生态学，还应考虑生理学。