Fig. 3. Rate of oxygen consumption (_O2) measurements throughout an experimental run with a 105 g triggerfish Rhinecanthus aculeatus. Measurements began shortly after placing the fish in the respirometer (19:50 h) and were made every 10 min. _O2 stabilized overnight, allowing determination of standard metabolic rate (see text). Three periods of spontaneous activity appeared in the early morning hours, demonstrating the high resolution of the system. The shaded region indicates the period during the swimming speed test.