Data in this article presents data (means and standard deviations) for prey biomass from essential feeding habitats for the endangered western gray whale. Prey include Actinopterygii (primarily the sand lance Ammodytes hexapterus), Amphipoda, Bivalvia, Cumacea, Isopoda, and Polychaeta. Total prey biomass (sum of the six prey groups) is also presented. Statistical analyses document spatial and temporal trends in prey biomass concentrations. Multivariate analyses using canonical correspondence analysis characterize relationships of potential drivers of community changes.