Fig. 4From: Circadian behaviour of Tectus (Trochus) niloticus in the southwest Pacific inferred from accelerometryMean power spectra (Lomb–Scargle procedure) for light intensity and number of identified movements. Light intensity (black lines) and movements (grey lines) were summed for 10 topshells over 30-min interval in New Caledonia (a) and Vanuatu (b). Dotted lines, p < 0.001. The main spectral peak corresponded to a period of 23.15 h, and secondary spectral peaks to harmonic frequencies at 8 h and 12 hBack to article page