Long-term time-series of Atlantic salmon catches for c. 250 Norwegian rivers (some spanning the period 1876 to present) and 48 Scottish rivers (1952 to present) will be subject to statistical analyses in order to deduce what regulates the long-term dynami cs of spawning populations. Preliminary analyses confirm that the catch data contain biologically interpretable signals. These analyses also indicate clear negative trends for Scottish salmon especially in recent years but trends for Norwegian rivers are highly spatially variable among rivers and regions. The temporal correlation between time series appears to vary over time, with trends persisting over several decades, while the spatial correlation appears relatively short range. We aim to consolidate th ese preliminary analyses and extend them to a consideration of mechanisms by pinpointing the factors generating differences in spatial trends for production and spatial variations in the trends. We aim to identify what types of climatic (local, regional, large-scale, river-based or marine-based) factors most strongly influence catches in various rivers and regions, and pinpoint mechanisms that might be at work, at sea or in fresh water. This approach will require advanced statistical methodology and will incorporate additional time series for climatic (density-independent) and biological (mainly density dependent) variables. The use of the combined national catch data is strategic, since it will generate a particularly wide latitudinal spread and a corre spondingly powerful template for analysis and interpretation. Biological interpretation of population-specific findings will generate insights required to predict the impacts of current climate change scenarios on Atlantic salmon populations. Prediction w ill facilitate future management of the resource.