Fig. 1. (A–G) Effect of developmental stage and hypoxia on dissolved oxygen (DO) concentration in the boundary layer of rainbow trout embryos before hatching relative to distance to the chorion (A–E) and in larvae after hatching relative to the distance to the skin (F,G). Boundary layers were measured in normoxic water (100% sat, black circles and black lines) and after 30 min exposure to hypoxic water (35% sat, red triangles and red lines). Numbers beside panel letters indicate developmental time in days post fertilization (d.p.f.). Values are means ± s.e.m., N=8; different animals were used at each developmental stage and different animals were used in normoxia vs hypoxia. (H,I) The boundary layer gradient, (the difference between the DO in the free-stream and the DO at the surface; H) and the boundary layer thickness (BLT; I), were calculated from the boundary layer curves in A–G, and are plotted against developmental time (d.p.f.). Vertical broken line indicates approximate time of hatching.