To determine whether differences in cockle density or qualitative burial depth observed during the 2014 field survey were affected by green macroalgal (GMA) mats, we conducted a field caging experiment whereby cockles were subjected to the presence or absence of simulated GMA mats for 12 weeks (July-September 2014). This dataset contains all data collected during that field experiment. This dataset is associated with the following publication: Lewis, N., and T. DeWitt. Effect of Green Macroalgal Blooms on the Behavior, Growth, and Survival of Cockles (Clinocardium nuttallii) in Pacific NW Estuaries. MARINE ECOLOGY PROGRESS SERIES. Inter-Research, Luhe, GERMANY, 582: 105-120, (2017).