Fig. 6. (A) The number of movements min^–1 by 44 d.p.f. rainbow trout larvae in normoxic water (first open circle), then exposed to 35% sat for 4 h (closed circles), and then returned (vertical broken line) to normoxic water for a further 2 h (open circles). Values are means ± s.e.m. (N=9). The effect of exposure to hypoxia was reversible, but there was a delay of about 30 min and then a gradual return to pre-exposure levels. (B) Time course of the change in DO (% sat) in the free-stream around the larvae while movements were being recorded.