Social learning can be fundamental to cohesive group living, and for many schooling fishes, inter-generational information transfer is considered a vital ingredient underpinning movement decisions. Yet key information is often missing on the spatial outcomes of such decisions, and the collective’s role in shaping migratory traditions remains uncertain. To explore these issues, we focused on Atlantic herring (Clupea harengus), a long-lived, dense-schooling species, noted for its unpredictable shifts in winter distribution, and developed space-time regression models of wintering dynamics around Iceland over 23 years. We included covariates reflecting local-scale environmental factors, recent fishing activity, and two proxies for spatial ‘memory’ of past wintering sites. The previous winter’s occurrence pattern was a strong predictor of the present pattern, its influence increasing with adult population size. We propose that a ‘wisdom of the crowd’ dynamic may be operating, by which navigational accuracy improves in larger, better synchronized schools. Wintering herring also preferred warmer, fresher waters, close to hotspots of summer zooplankton biomass, our results indicative of heightened environmental sensitivity in younger cohorts. Predictions one-year ahead illustrate the value of uniting demographic information and non-stationary models to quantify the strength of collective memory in animal groups, and its relevance for spatial management directives.