Fig. 1: Analysis of empirical data of the surface-wave activity.
From: Fish shoals resemble a stochastic excitable system driven by environmental perturbations
a, Localization of the field site in Teapa, Tabasco. The main pond, where all the videos were taken, is marked in the inset of the map. b, Snapshots of the rectification and background subtraction processes performed on the empirical videos. Active pixels caused by the disturbance of the surface as fish dive down are depicted in white. c, Plot of one surface-activity signal \({{{\mathcal{A}}}}{(t)}\) that is representative for all empirical videos. The inset serves to visualize the inter-spike time τ1 and the spike-duration time τ2. d,e, Plots of the distributions of the characteristic times P(τ1) (d) and P(τ2) (e) obtained from the empirical data. Both distributions are consistent with gamma distributions, which have exponentially decaying tails (KS statistic, p = 0.013 and p = 0.034, respectively), shown as black dashed lines. f, Plot of the distribution of the cluster areas P(a) obtained from the empirical data. The power-law fit (black dashed line) was estimated following ref. 30 (KS statistic, p = 0.044). For spatial scales ranging from 10−1 m2 up to 102 m2, the exponent is found to be αa ≈ 2.3. See Methods for details on the goodness-of-fit for all empirical distributions.
