Ontogenetic shifts represent important transitions that can influence how fish interact with their environment. However, ontogenetic shifts are rarely placed into a population context due to the difficulty of incorporating the vagaries of size-mediated interactions. As such, we evaluated the role of ontogenetic shifts in diet as they relate to potential competitive interactions between kokanee Oncorhynchus nerka and Opossum Shrimp Mysis diluviana (hereafter Mysis) in Lake Pend Oreille, Idaho. Contemporary data were used to understand diet patterns of Mysis and kokanee. Historical data were evaluated within the context of ontogenetic shifts to better understand the long-term, population-level ramifications of interactions between Mysis and kokanee. Diet analysis revealed age-specific divergences in diet whereby juvenile kokanee primarily consumed copepods and adult kokanee preferentially consumed cladocerans. When placed in a historical context, age-specific patterns in kokanee diet likely led to increases in adult growth following declines in Mysis abundance. Improved fitness of adult fish likely resulted in record high abundances of kokanee in Lake Pend Oreille thereby shifting the balance from inter- to intraspecific competition.

中文翻译：

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个体遗传饮食的变化对 kokanee-Mysis diluviana 系统中资源竞争的潜在影响

个体发生变化代表了重要的转变，可以影响鱼类与环境的相互作用。然而，由于难以纳入大小介导的相互作用的变幻莫测，个体发生变化很少被置于种群背景中。因此，我们评估了个体发生变化在饮食中的作用，因为它们与爱达荷州彭德奥雷尔湖的 kokanee Oncorhynchus nerka 和负鼠虾米西斯 diluviana（以下简称 Mysis）之间的潜在竞争相互作用有关。当代数据被用来了解糠虾和可卡尼的饮食模式。在个体发生变化的背景下评估历史数据，以更好地了解 Mysis 和 kokanee 之间相互作用的长期、种群水平的影响。饮食分析揭示了饮食中特定年龄的差异，其中幼年 kokanee 主要食用桡足类，而成年 kokanee 则优先食用枝角类动物。当放在历史背景下时，kokanee 饮食中特定于年龄的模式可能会导致在 Mysis 丰度下降后成人生长增加。提高成年鱼的适应性可能导致彭德奥雷尔湖中 kokanee 的丰度创历史新高，从而将平衡从种间竞争转移到种内竞争。