Seasonal Utilization Distributions (UDs) of bluefin tuna.
The locations of the tuna were examined for the (A) spawning period (i.e. May 15 to July 15) and the seasonal periods of (B) spring, (C) summer, (D) autumn and (E) winter. UDs were computed using the Kernel method through the ad hoc method (h = Sigma*n^(-1/6), Sigma = 0.5*(sd(x)+sd(y))). The graphs show the UDs cumulative frequencies up to 95% (the color attributed to a given percentage p applies to areas comprised between p and p–1% isopleths).