Fig. 7. Mean of all the observed maximal ascent and descent speeds (± s.e.m) during vertical excursions for (from left to right) Fish 390, Fish 392, Fish 301, Fish 298, Fish 625, Fish 241 and Fish 224, plotted as a function of size (fork length, FL). The regression lines were fitted with a weighted linear least-square procedure using the reciprocals of the s.e.m. as weight and are: y=3.627–0.0192x (for descents, r²=0.985, P=0.00015) and y=3.439–0.0195x (for ascents, r²=0.945, P=0.001). Note that the s.e.m. for each point is so small that it is not distinguishable from the symbol. Also the maximal vertical speeds observed for each fish during their entire tag deployment period are shown (filled triangles).