The goal of this study was to determine whether trout stocking affects phytoplankton abundance and the occurrence of toxic cyanobacteria blooms in Washington lakes. The trophic cascade effect of trout stocking in Washington lakes was evaluated through key findings from a literature review, by compiling existing water quality, cyanobacteria toxin, and trout stocking databases, and by evaluating relationships among the key variables on a seasonal and annual basis using statistical analyses. Two different data sets were used for this study that included Liberty Lake.