Diadromy in freshwater animals enriches in biodiversity and enhances local nutrient cycling. Several hypotheses has been proposed previously to understand downstream change in lotic biota and ecosystem metabolism, interaction between anadromy/catadromy and latitudinal gradient in biological productions (BPs) over freshwater and ocean, and reciprocal subsidization between aquatic and riparian systems along seasonal shift of each BPs. Here we propose a synthetic conceptual model to understand the food availability against lotic consumers, by considering simultaneously 1) variation in terrestrial vegetation-climate complex, which is known as Keppen and Geiger’s classification, 2) seasonality and downstream change in BPs from aquatic and riparian, and 3) latitudinal gradients in BPs in lotic/coastal. We could be summarized downstream changes in the set of several parameters that regulating BP for aquatic animals, by expressed as amount of organic matter inputs, at each climate-vegetation complex. Although comprehensive data sets to test the hypothesis are not available, recent advances on remote sensing, GIS and database could contribute to estimating primary and secondary BPs in aquatic and riparian ecosystems.