<p>The occurrence of anadromy in fish is partly influenced by how marine and freshwater primary productivities covary locally. Once at sea, anadromous fish may be exposed to large spatial variations in marine productivity having potential fitness-related effects. Here, anadromous Arctic charr (<i>Salvelinus alpinus</i>) from Nunavik, Québec, Canada, were monitored during their upstream migration and their condition, growth, survival, and the reproductive status of females were quantified from sampled specimens. Nearby marine productivity was positively associated with condition, but not growth. Current-year female spawners were infrequent in rivers known to be used for spawning, whereas none were captured at other sampling locations for which the presence of spawning grounds was uncertain. Female fork length, but not condition, was positively associated with spawning probability, whereas length-at-maturity estimates were positively related to marine productivity. Survival was positively influenced by the boating distance between a river mouth and the nearest Inuit community, but negatively related to the size of the community. Contrasting results were observed for anadromous charr frequenting more- or less-productive marine environments, with the former generally exhibiting better condition and faster growth, but experiencing lower spawning and survival probabilities, and the latter showing the opposite pattern. Given the difficulties associated with explaining observed phenotypic plasticity in Arctic charr, the implementation of long-term monitoring programs, as opposed to single-year studies, may constitute a better approach to deepening our understanding of how phenotypic and genotypic variation are linked to changing environmental conditions, especially in the face of the many and increasing direct and indirect anthropogenic stressors affecting this species across its distributional range.</p>