Partial migration represents an important yet often overlooked form of intraspecific diversity, where resident and migratory life histories coexist within a population. By distributing migratory strategies across habitats, seasons and environmental conditions, partial migration may generate portfolio effects that buffer fish populations against environmental variability. However, its contribution to climate resilience remains poorly understood and is likely context dependent. We first undertake a systematic review of how partial migration shapes connectivity and population responses to climate change, investigating whether contrasting migratory contingents may differ in ecological and demographic outcomes. We then demonstrate how elemental and isotopic markers in otoliths and eye lenses can resolve these processes using black bream (Acanthopagrus butcheri) from the Coorong Lagoon, South Australia. Lifetime otolith Ba profiles reconstructed differing estuarine resident and migrant movement strategies, while eye-lens stable isotopes highlighted variations in lifetime dietary trajectories and trophic ecology. Together, these complementary markers revealed links between movement outcomes, trophic ecology and annual variation in environmental conditions. Ultimately, the chemical and isotopic composition of archival tissues can provide key insights on trade-offs and outcomes from differing migratory strategies, help identify the environmental drivers of migratory diversity, and improve our understanding of fish population resilience in an era of accelerated change.