Fig. 7. Mean values of vertical rate, swimming speed, body angle and tailbeat frequency per 1 m depth change for the initial, middle and final 5 m ranges of vertical movements whose total change of depth was greater than 25 m for salmon 9902 and 9904. Values are means ± S.E.M. The left panels shows descents (N=9) that started from the surface water (5 m deep) and the right panel shows ascents (N=13) that finished in the surface water. Apart from swimming speed, all behavioural variables changed significantly with respect to the change in the range of vertical travel (Friedman’s test).