Schematic figure of our method for incorporating the effect of currents on distance between patches. Panel a depicts the turtle at time 1 and a candidate patch at time 2. Distance d is the Euclidean distance separating the patches. The light grey lines depict the N-S surface current vector (v
), and the E-W current vector (u
). Panel b depicts the new position of the candidate patch after the currents have been subtracted; distance d’ reflects the new distance between the turtle and the patch after currents have been accounted for.