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Abstract Trophic interactions operate across the lifetime of an individual organism, yet our understanding of these processes is largely limited to a single life stage or moment in time. Management and conservation implications of this knowledge gap are particularly important, given the mounting number, spread, and ecological impacts of invasive species. Biotracers, such as carbon and nitrogen stable isotopes of animal muscle, are commonly used to characterize the trophic ecology of an individual but fail to capture intraindividual variation and ontogenetic dietary shifts. However, recent work suggests that eye lenses may facilitate the reconstruction of individual lifetime trophic trajectories for fishes, including the chronology of past trophic positions of and carbon flow to consumers. By combining stable isotope analysis of fish eye lens tissue with aging techniques (otolith growth measurements), this study is the first to ask how the lifetime trophic niches of individuals vary within different community contexts. The results provide evidence for asymmetric competition causing differing trajectories in lifetime trophic niches for native and nonnative fishes along an invasion gradient in Burro Creek, Arizona, USA. Native roundtail chub, Sonora sucker, and desert sucker all displayed a coordinated displacement of lifetime trophic trajectories to a lower trophic level and reliance on aquatic, rather than terrestrial, resources as indicated by a shift to lower δ¹³C and δ¹⁵N in mixed, relative to native‐only, communities. By contrast, the trophic trajectories of nonnative green sunfish and bullhead species remained consistent between native and nonnative dominated communities. The presence of nonnative species led to a significantly greater decrease in δ¹³C through ontogeny for roundtail chub, a species of conservation concern in Arizona. These results demonstrate the prolonged trophic impact of nonnative fishes on native fishes beyond a single life stage. Displacement of ontogenetic dietary shifts by native fishes through interactions with nonnative species may lead to reduced fish growth and fitness, with implications at the population and ecosystem levels. Stable isotope analysis of fish eye lens tissue offers new opportunities to study the lifetime chronology of individual feeding habits and allows for exploration of the impacts of invasive species and environmental change throughout ontogeny. 

Abstract The global spread of invasive species in aquatic ecosystems has prompted population control efforts to mitigate negative impacts on native species and ecosystem functions. Removal programs that optimally allocate removal effort across space and time offer promise for improving invader suppression or eradication, especially given the limited resources available to these programs. However, science‐based guidance to inform such programs remains limited. This study leverages two intensive fish removal programs for nonnative green sunfish (Lepomis cyanellus) in intermittent streams of the Bill Williams River basin in Arizona, USA, to explore alternative management strategies involving variable allocation of removal effort in time and space and compare static versus dynamic decision rules. We used Bayesian hierarchical modeling to estimate demographic parameters using existing removal data, with evidence that both removal programs led to at least a 0.39 probability of eradication. Simulated alternative management strategies revealed that population suppression, but not eradication, could be achieved with reduced effort and that dynamic management practices that respond to species abundance in real time can improve the efficiency of removal efforts. High removal frequency and program duration, including continued monitoring after zero fish were captured, contributed to successful population control. With management efforts struggling to keep pace with the rising spread and impacts of invasive species, this research demonstrates the utility of quantitative removal models to help improve invasive removal programs and robustly evaluate the success of population suppression and eradication.