Studies of resource tracking typically compare the date an animal uses a given location with the date of optimal resource availability at the same location (9⇓–11, 18, 87). We used linear mixed-effects regression to evaluate the relationships between the date of blue whale use and the date of peak productivity (lagged by 1 mo), while controlling for SST, for (i) each year (to reflect current conditions), and (ii) the mean climatology. Individuals were nested as a random effect. We repeated analyses using tracks from the simulated random migrants. We tested for similarity between the distributions of contemporaneous, long-term mean, and long-term SD chlorophyll values at foraging locations and those available in the environment using the Bhattacharyya similarity coefficient, which ranges from 0 (no overlap in distributions) to 1 (perfect overlap), and tested for significance using Kolmogorov–Smirnov tests and Welch t tests. All spatial and statistical analyses were conducted in R 3.4.1 (88).