Offshore re-oligotrophication has become one of the most recent concerns in regard to the natural resource management in lakes around the world. While total phosphorus (TP) is still considered to be a critical determinant of freshwater ecosystem productivity, confounding effects of multiple factors (i.e., phosphorus loading reduction, extreme weather, climate change, land use changes in the watershed, implementation of biomanipulations, and introduction of invasive species) can alter energy pathways, making the management decisions difficult. Regardless it is intentional or not, substantial phosphorus control in many lakes and rivers revert their trophic status towards the oligotrophic level to the extent that the primary productivity can no longer support pelagic ecosystem and in turn local fisheries. Our analysis is based on a long-term monitoring dataset (1975–2013) from the Bay of Quinte, Lake Ontario, Canada that contains regularly sampled water quality, primary producers, consumers through food web to fish. We used Structural Equation Models (SEMs) with Bayesian hierarchical approach to examine the potential impacts of re-oligotrophication on the fish community while accounting for the shifts in energy pathways through food-web under dreissenids mussels mediated environmental conditions. Our Bayesian hierarchical SEMs identified that stronger reliance of primary productivity on the ambient TP concentrations after the dreissenids invasion. However, the strength of the relationships varied among algal groups, and weaker towards higher trophic level organisms’ groups. Our SEM also estimated much smaller fish biomass loss via further reduction of TP, projecting 6.4 % reduction of top-predatory fish dominated by the walleye (Sander vitreus), while previous similar attempt estimated 22.2% reduction (Hossain et al., 2019). Our modeling analysis highlighted the importance of food-web cascade in assessing the resource – ecosystem productivity relationship, which ultimately support the realistic target and the success of ecosystem and fishery restoration.